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<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">Front. Psychiatry</journal-id>
<journal-title>Frontiers in Psychiatry</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Psychiatry</abbrev-journal-title>
<issn pub-type="epub">1664-0640</issn>
<publisher>
<publisher-name>Frontiers Media S.A.</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.3389/fpsyt.2025.1606743</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Psychiatry</subject>
<subj-group>
<subject>Systematic Review</subject>
</subj-group>
</subj-group>
</article-categories>
<title-group>
<article-title>Poor sleep quality among patients with Parkinson&#x2019;s disease: a meta-analysis and systematic review</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author" equal-contrib="yes">
<name>
<surname>Si</surname>
<given-names>Tong Leong</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<xref ref-type="author-notes" rid="fn003">
<sup>&#x2020;</sup>
</xref>
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</contrib>
<contrib contrib-type="author" equal-contrib="yes">
<name>
<surname>Wang</surname>
<given-names>Yue-Ying</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
<xref ref-type="author-notes" rid="fn003">
<sup>&#x2020;</sup>
</xref>
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</contrib>
<contrib contrib-type="author" equal-contrib="yes">
<name>
<surname>Li</surname>
<given-names>Jia-Xin</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
<xref ref-type="author-notes" rid="fn003">
<sup>&#x2020;</sup>
</xref>
<role content-type="https://credit.niso.org/contributor-roles/data-curation/"/>
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</contrib>
<contrib contrib-type="author" equal-contrib="yes">
<name>
<surname>Bai</surname>
<given-names>Wei</given-names>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
<xref ref-type="author-notes" rid="fn003">
<sup>&#x2020;</sup>
</xref>
<uri xlink:href="https://loop.frontiersin.org/people/2615230/overview"/>
<role content-type="https://credit.niso.org/contributor-roles/data-curation/"/>
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</contrib>
<contrib contrib-type="author">
<name>
<surname>Sun</surname>
<given-names>He-Li</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
<role content-type="https://credit.niso.org/contributor-roles/writing-review-editing/"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Rao</surname>
<given-names>Shu-Ying</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<uri xlink:href="https://loop.frontiersin.org/people/3071655/overview"/>
<role content-type="https://credit.niso.org/contributor-roles/data-curation/"/>
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</contrib>
<contrib contrib-type="author">
<name>
<surname>Zhu</surname>
<given-names>Han-Yu</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<role content-type="https://credit.niso.org/contributor-roles/data-curation/"/>
<role content-type="https://credit.niso.org/contributor-roles/writing-review-editing/"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Ungvari</surname>
<given-names>Gabor S.</given-names>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
<xref ref-type="aff" rid="aff6">
<sup>6</sup>
</xref>
<uri xlink:href="https://loop.frontiersin.org/people/1554975/overview"/>
<role content-type="https://credit.niso.org/contributor-roles/writing-review-editing/"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Su</surname>
<given-names>Zhaohui</given-names>
</name>
<xref ref-type="aff" rid="aff7">
<sup>7</sup>
</xref>
<uri xlink:href="https://loop.frontiersin.org/people/1046370/overview"/>
<role content-type="https://credit.niso.org/contributor-roles/data-curation/"/>
<role content-type="https://credit.niso.org/contributor-roles/writing-review-editing/"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Cheung</surname>
<given-names>Teris</given-names>
</name>
<xref ref-type="aff" rid="aff8">
<sup>8</sup>
</xref>
<uri xlink:href="https://loop.frontiersin.org/people/565626/overview"/>
<role content-type="https://credit.niso.org/contributor-roles/data-curation/"/>
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</contrib>
<contrib contrib-type="author" corresp="yes">
<name>
<surname>Ng</surname>
<given-names>Chee H.</given-names>
</name>
<xref ref-type="aff" rid="aff9">
<sup>9</sup>
</xref>
<xref ref-type="author-notes" rid="fn001">
<sup>*</sup>
</xref>
<uri xlink:href="https://loop.frontiersin.org/people/501255/overview"/>
<role content-type="https://credit.niso.org/contributor-roles/conceptualization/"/>
<role content-type="https://credit.niso.org/contributor-roles/writing-review-editing/"/>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name>
<surname>Xiang</surname>
<given-names>Yu-Tao</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
<xref ref-type="author-notes" rid="fn001">
<sup>*</sup>
</xref>
<uri xlink:href="https://loop.frontiersin.org/people/797822/overview"/>
<role content-type="https://credit.niso.org/contributor-roles/conceptualization/"/>
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<role content-type="https://credit.niso.org/contributor-roles/writing-review-editing/"/>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name>
<surname>Wang</surname>
<given-names>Gang</given-names>
</name>
<xref ref-type="aff" rid="aff10">
<sup>10</sup>
</xref>
<xref ref-type="author-notes" rid="fn001">
<sup>*</sup>
</xref>
<uri xlink:href="https://loop.frontiersin.org/people/2558488/overview"/>
<role content-type="https://credit.niso.org/contributor-roles/data-curation/"/>
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</contrib>
</contrib-group>
<aff id="aff1">
<sup>1</sup>
<institution>Macao Observatory for Social Development, University of Saint Joseph</institution>, <addr-line>Macao</addr-line>,&#xa0;<country>Macao SAR, China</country>
</aff>
<aff id="aff2">
<sup>2</sup>
<institution>Unit of Psychiatry, Department of Public Health and Medicinal Administration, Institute of Translational Medicine, Faculty of Health Sciences, University of Macau</institution>, <addr-line>Macao</addr-line>,&#xa0;<country>Macao SAR, China</country>
</aff>
<aff id="aff3">
<sup>3</sup>
<institution>Centre for Cognitive and Brain Sciences, University of Macau</institution>, <addr-line>Macao</addr-line>,&#xa0;<country>Macao SAR, China</country>
</aff>
<aff id="aff4">
<sup>4</sup>
<institution>Department of Epidemiology and Biostatistics, School of Public Health, Jilin University</institution>, <addr-line>Changchun</addr-line>,&#xa0;<country>China</country>
</aff>
<aff id="aff5">
<sup>5</sup>
<institution>Section of Psychiatry, University of Notre Dame Australia</institution>, <addr-line>Fremantle, WA</addr-line>,&#xa0;<country>Australia</country>
</aff>
<aff id="aff6">
<sup>6</sup>
<institution>Division of Psychiatry, School of Medicine, University of Western Australia</institution>, <addr-line>Perth, WA</addr-line>,&#xa0;<country>Australia</country>
</aff>
<aff id="aff7">
<sup>7</sup>
<institution>School of Public Health, Southeast University</institution>, <addr-line>Nanjing</addr-line>,&#xa0;<country>China</country>
</aff>
<aff id="aff8">
<sup>8</sup>
<institution>School of Nursing, Hong Kong Polytechnic University</institution>, <addr-line>Hong Kong</addr-line>,&#xa0;<country>Hong Kong SAR, China</country>
</aff>
<aff id="aff9">
<sup>9</sup>
<institution>Department of Psychiatry, The Melbourne Clinic and St Vincent&#x2019;s Hospital, University of Melbourne</institution>, <addr-line>Richmond, VIC</addr-line>,&#xa0;<country>Australia</country>
</aff>
<aff id="aff10">
<sup>10</sup>
<institution>Beijing Key Laboratory of Mental Disorders, National Clinical Research Center for Mental Disorders &amp; National Center for Mental Disorders, Beijing Anding Hospital, Capital Medical University</institution>, <addr-line>Beijing</addr-line>,&#xa0;<country>China</country>
</aff>
<author-notes>
<fn fn-type="edited-by">
<p>Edited by: Luigi De Gennaro, Sapienza University of Rome, Italy</p>
</fn>
<fn fn-type="edited-by">
<p>Reviewed by: Caterina Leitner, Vita-Salute San Raffaele University, Italy</p>
<p>Loida Camargo, University of Cartagena, Colombia</p>
</fn>
<fn fn-type="corresp" id="fn001">
<p>*Correspondence: Chee H. Ng, <email xlink:href="mailto:cng@unimelb.edu.au">cng@unimelb.edu.au</email>; Yu-Tao Xiang, <email xlink:href="mailto:xyutly@gmail.com">xyutly@gmail.com</email>; Gang Wang, <email xlink:href="mailto:gangwangdoc@ccmu.edu.cn">gangwangdoc@ccmu.edu.cn</email>
</p>
</fn>
<fn fn-type="equal" id="fn003">
<p>&#x2020;These authors have contributed equally to this work</p>
</fn>
</author-notes>
<pub-date pub-type="epub">
<day>16</day>
<month>07</month>
<year>2025</year>
</pub-date>
<pub-date pub-type="collection">
<year>2025</year>
</pub-date>
<volume>16</volume>
<elocation-id>1606743</elocation-id>
<history>
<date date-type="received">
<day>16</day>
<month>05</month>
<year>2025</year>
</date>
<date date-type="accepted">
<day>26</day>
<month>06</month>
<year>2025</year>
</date>
</history>
<permissions>
<copyright-statement>Copyright &#xa9; 2025 Si, Wang, Li, Bai, Sun, Rao, Zhu, Ungvari, Su, Cheung, Ng, Xiang and Wang</copyright-statement>
<copyright-year>2025</copyright-year>
<copyright-holder>Si, Wang, Li, Bai, Sun, Rao, Zhu, Ungvari, Su, Cheung, Ng, Xiang and Wang</copyright-holder>
<license xlink:href="http://creativecommons.org/licenses/by/4.0/">
<p>This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</p>
</license>
</permissions>
<abstract>
<sec>
<title>Objective</title>
<p>Poor sleep quality is common among patients with Parkinson&#x2019;s disease (PD), although the reported prevalence rates vary between studies. This meta-analysis examined the overall prevalence of poor sleep quality in patients with PD and identified potential factors contributing to the differences in prevalence across studies.</p>
</sec>
<sec>
<title>Methods</title>
<p>Both PRISMA and MOOSE guidelines were applied in this meta-analysis. A systematic search was conducted in PubMed, EMBASE, PsycINFO, Web of Science, CNKI and Wangfang from their inception to November 4, 2023. Studies were selected based on predefined PICOS criteria (i.e., PD patients, prevalence of poor sleep quality, cross-sectional/cohort designs). Study quality/risk of bias was assessed using a standardized 8-item tool. Pooled prevalence was calculated sources of heterogeneity (e.g., age, sex, depression, anxiety, cognition scores, disease severity, and medication dose) were explored via subgroup and meta-regression analyses. A random-effects model was utilized to calculate the overall prevalence and corresponding 95% confidence intervals (CIs).</p>
</sec>
<sec>
<title>Results</title>
<p>In total, 63 studies involving 9,382 PD patients were included. The overall prevalence of poor sleep quality was 58.07% (95% CI: 54.26&#x2013;61.88%). Higher rates were related to various factors including studies from Europe &amp; Central Asia, Upper middle income countries, mixed patient sources, lower diagnostic cutoffs, and use of Movement Disorder Society PD criteria. Meta-regression analysis showed that late onset PD was associated with poorer sleep quality in patients with PD.</p>
</sec>
<sec>
<title>Conclusion</title>
<p>Poor sleep quality is common in PD patients. Regular monitoring of sleep quality and promotion of sleep hygiene should be prioritized in the management of patients with PD. Additionally, further research on sleep and PD is warranted in low- and middle-income countries to ensure the applicability of findings across diverse populations.</p>
</sec>
<sec>
<title>Systematic Review Registration</title>
<p>
<uri xlink:href="https://inplasy.com/inplasy-2023-10-0022/">https://inplasy.com/inplasy-2023-10-0022/</uri>, identifier INPLASY2023100022.</p>
</sec>
</abstract>
<kwd-group>
<kwd>Parkinson&#x2019;s disease</kwd>
<kwd>sleep quality</kwd>
<kwd>meta-analysis</kwd>
<kwd>prevalence</kwd>
<kwd>epidemiology</kwd>
</kwd-group>
<counts>
<fig-count count="2"/>
<table-count count="3"/>
<equation-count count="0"/>
<ref-count count="135"/>
<page-count count="19"/>
<word-count count="7561"/>
</counts>
<custom-meta-wrap>
<custom-meta>
<meta-name>section-in-acceptance</meta-name>
<meta-value>Sleep Disorders</meta-value>
</custom-meta>
</custom-meta-wrap>
</article-meta>
</front>
<body>
<sec id="s1" sec-type="intro">
<label>1</label>
<title>Introduction</title>
<p>Parkinson&#x2019;s disease (PD) is a progressive neurological disorder that interferes with the initiation and execution of voluntary movement, resulting in difficulty performing basic activities of daily living (<xref ref-type="bibr" rid="B1">1</xref>). PD is an age-related condition as its prevalence steadily increases with age (<xref ref-type="bibr" rid="B2">2</xref>). Although the cause is still unknown, many researchers believe that the disease is determined by the interaction between genetic and environmental factors, leading to a gradual degeneration of neurons in susceptible areas of the brain (<xref ref-type="bibr" rid="B2">2</xref>). Apart from the typical motor symptoms, non-motor symptoms in patients with PD, including sleep problems, autonomic dysfunction and sensory abnormalities (<xref ref-type="bibr" rid="B3">3</xref>), also have a significant impact on quality of life and overall health (<xref ref-type="bibr" rid="B4">4</xref>, <xref ref-type="bibr" rid="B5">5</xref>).</p>
<p>Sleep problems in PD patients, such as poor sleep quality, are among the most prominent non-motor symptoms that considerably impact on the quality of life in both patients and caregivers (<xref ref-type="bibr" rid="B6">6</xref>, <xref ref-type="bibr" rid="B7">7</xref>). The causes of sleep problems in PD patients involve disease-related factors such as dopaminergic medications, co-morbid mood disorders, and other related factors (<xref ref-type="bibr" rid="B8">8</xref>), as well as the associated symptoms and treatments of PD (<xref ref-type="bibr" rid="B9">9</xref>).</p>
<p>Poor sleep quality is one of the major sleep problems experienced by PD patients (<xref ref-type="bibr" rid="B10">10</xref>). Sleep quality is defined as one&#x2019;s satisfaction with sleep experience, encompassing aspects such as sleep onset, sleep maintenance, subjective sleep quality, and mental state upon awakening (<xref ref-type="bibr" rid="B11">11</xref>). Both subjective and objective methods can be employed to assess sleep quality. Objective techniques usually have a high reliability in collecting sleep parameter data, such as using actigraphy and polysomnography (<xref ref-type="bibr" rid="B12">12</xref>). However, these objective sleep quality tests are costly, time-consuming, not easily accessible by most practitioners, and unsuitable for use in epidemiological studies and clinical practice (<xref ref-type="bibr" rid="B13">13</xref>). As such, subjective measures on sleep quality have been developed for such purposes, for instance, the Pittsburgh Sleep Quality Index (PSQI). The PSQI is the most utilized subjective measurement of sleep quality across different populations, providing scores that allow for categorization as &#x201c;good&#x201d; or &#x201c;poor&#x201d; (<xref ref-type="bibr" rid="B14">14</xref>, <xref ref-type="bibr" rid="B15">15</xref>). In addition, the Parkinson&#x2019;s Disease Sleep Scale (PDSS) is another widely used visual analog scale that addresses several symptoms associated with sleep disorders in PD, including sleep quality (<xref ref-type="bibr" rid="B16">16</xref>).</p>
<p>Previous studies on the prevalence of poor sleep quality in patients with PD have reported rates ranging from 20% to 88% (<xref ref-type="bibr" rid="B17">17</xref>&#x2013;<xref ref-type="bibr" rid="B19">19</xref>). In addition, poor sleep quality in PD patients has been found to be associated with more severe comorbid depressive and anxiety symptoms, reduced cognitive performance, and more severe PD symptoms (<xref ref-type="bibr" rid="B20">20</xref>). Therefore, to address the negative impact of poor sleep quality on PD patients, it is important to understand the epidemiological patterns of poor sleep quality and its associated factors in this population.</p>
<p>To date, no systematic review and meta-analysis have been published on the prevalence estimates of poor sleep quality in PD patients. To address this gap, this meta-analysis aimed to assess the global prevalence of poor sleep quality in PD patients and identify potential factors contributing to the differences in prevalence in this population.</p>
</sec>
<sec id="s2">
<label>2</label>
<title>Method</title>
<sec id="s2_1">
<label>2.1</label>
<title>Search strategy</title>
<p>The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and Meta-analyses Of Observational Studies in Epidemiology (MOOSE) checklist were followed in conducting this meta-analysis (<xref ref-type="bibr" rid="B21">21</xref>). Three investigators (TLS, YYW and JXL) systematically and independently searched literature in the PubMed, EMBASE, PsycINFO, Web of Science, China National Knowledge Infrastructure (CNKI) and Wangfang databases from their inception date until November 4, 2023, using the following search items: &#x201c;Parkinson disease &#x201c; AND (&#x201c;Sleep Quality&#x201d; OR &#x201c;Qualities, Sleep&#x201d; OR &#x201c;Quality, Sleep&#x201d; OR &#x201c;Sleep Qualities&#x201d; OR &#x201c;quality of sleeping&#x201d; OR &#x201c;sleeping quality&#x201d; OR &#x201c;Pittsburgh sleep quality index&#x201d; OR &#x201c;PSQI&#x201d;) AND (&#x201c;prevalence&#x201d; OR &#x201c;epidemiology&#x201d; OR &#x201c;rate&#x201d;). The study protocol was registered with the International Platform of Registered Systematic Review and Meta-analysis Protocols (INPLASY; registration number: INPLASY2023100022).</p>
</sec>
<sec id="s2_2">
<label>2.2</label>
<title>Inclusion and exclusion criteria</title>
<p>The same three investigators (TLS, YYW and JXL) independently reviewed the titles and abstracts of relevant publications and then read the full texts of to assess eligibility. The inclusion criteria were developed using the PICOS acronym: Participants (P): patients with PD according to study-defined diagnostic criteria, such as the UK PD Society Brain Bank criteria (<xref ref-type="bibr" rid="B22">22</xref>) and the Movement Disorder Society (MDS) clinical diagnostic criteria for PD (<xref ref-type="bibr" rid="B23">23</xref>); Intervention (I): not applicable; Comparison (C): NR; Outcome (O): prevalence of poor sleep quality or having information that could generate an estimation of that prevalence, using standard tools, such as the PSQI, to measure the quality of the sleep; Study design (S): cross-sectional and cohort studies (only baseline data were analyzed in cohort studies) with accessible data published in English or Chinese journals. Exclusion criteria included reviews, systematic reviews, meta-analyses, case studies, and commentaries. Further, studies conducted specifically on PD samples with a primary sleep disorder (e.g., PD patients recruited from sleep clinics who suffered from insomnia disorder or obstructive sleep apnea (OSA)) were excluded to avoid the risk of overrepresenting sleep disturbances and selection bias in PD samples (<xref ref-type="bibr" rid="B24">24</xref>, <xref ref-type="bibr" rid="B25">25</xref>). Only the study with the most detailed information was included in the meta-analysis if a dataset was utilized in more than one study (<xref ref-type="bibr" rid="B26">26</xref>).</p>
</sec>
<sec id="s2_3">
<label>2.3</label>
<title>Data extraction and quality assessment</title>
<p>Participant and study data, such as the first author, publication year, sampling method, sleep quality measures, number of PD patients, cut-off value, illness duration, number of participants with poor sleep quality, and sleep quality scores, mean age and male proportion of study sample, diagnostic criteria, were extracted. Additionally, to characterize the multidimensional aspects of sleep, we extracted specific components from standardized sleep tools (e.g., the PSQI domains: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbance, use of sleep medications, and daytime dysfunction).</p>
<p>Such components including sleep medication use could enable the evaluation of naturally occurring sleep within broadly representative PD cohorts, rather than selective studies that focused on sleep comorbidities and effects of treatment.</p>
<p>Study quality was assessed using a standardized instrument for epidemiological studies (<xref ref-type="bibr" rid="B27">27</xref>, <xref ref-type="bibr" rid="B28">28</xref>) with the following eight items: (1) target population was defined clearly; (2) probability sampling or entire population surveyed; (3) response rate was &#x2265;80%; (4) non-responders were clearly described; (5) sample was representative of the target population; (6) data collection methods were standardized; (7) validated criteria were used to diagnose PD; and (8) prevalence estimates were given with confidence intervals (CIs) and detailed by subgroups. The total score ranged from 0 to 8. Studies with a total score of &#x201c;7&#x2013;8&#x201d; were considered as &#x201c;high quality,&#x201d; &#x201c;4&#x2013;6&#x201d; as &#x201c;moderate quality,&#x201d; and &#x201c;0&#x2013;3&#x201d; as &#x201c;low quality&#x201d; based on previous studies (<xref ref-type="bibr" rid="B25">25</xref>, <xref ref-type="bibr" rid="B29">29</xref>, <xref ref-type="bibr" rid="B30">30</xref>).</p>
</sec>
<sec id="s2_4">
<label>2.4</label>
<title>Statistical analyses</title>
<p>All the statistical analyses were conducted using R program (<xref ref-type="bibr" rid="B31">31</xref>). A random-effects model was used to synthesis the pooled prevalence of poor sleep quality and its 95% confidence intervals (95% CI) (<xref ref-type="bibr" rid="B32">32</xref>). <italic>I<sup>2</sup>
</italic> statistics were used to determine the degree of study heterogeneity, with 25%, 50%, and 75% tentatively indicating low, moderate, and high heterogeneity, respectively (<xref ref-type="bibr" rid="B33">33</xref>). Subgroup analyses for categorical variables (e.g., study regions, countries by economic status according to the World Bank&#x2019;s criteria (<xref ref-type="bibr" rid="B34">34</xref>), study design, cut-off value signifying poor sleep quality, and patients resources), and meta-regression analysis for continuous variables (mean age, proportions of male, depression, anxiety and cognitive dysfunction respectively, mean scores of MoCA, mean scores of MMSE and mean scores of Hoehn and Yahr Staging, mean levodopa equivalent daily dose and quality assessment score) were conducted to explore the sources of potential heterogeneity. The Egger&#x2019;s test was used to evaluate publication bias, and a visual funnel plot for asymmetry was also provided. If there was publication bias (<italic>P</italic>&lt;0.05), a trim-and-fill analysis was used. Sensitivity analyses were carried out to assess the stability of results by individually eliminating each study. The significance level was set at 0.05 (two-tailed).</p>
</sec>
</sec>
<sec id="s3" sec-type="results">
<label>3</label>
<title>Results</title>
<sec id="s3_1">
<label>3.1</label>
<title>Search results and study characteristics</title>
<p>Out of a total of 5,514 publications initially retrieved, 1,220 were excluded. The remaining 4,294 studies were screened for eligibility. By screening the titles and abstracts, we identified 451 potentially eligible studies. After screening the full text of these studies, we ultimately included 63 studies in this meta-analysis (see <xref ref-type="fig" rid="f1">
<bold>Figure&#xa0;1</bold>
</xref>).</p>
<fig id="f1" position="float">
<label>Figure&#xa0;1</label>
<caption>
<p>PRISMA flow diagram of study selection.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fpsyt-16-1606743-g001.tif">
<alt-text content-type="machine-generated">Flowchart detailing the process of identifying studies via databases and registers. Initially, 5,514 records were identified from databases like PubMed and CNKI. After removing 1,220 records for reasons such as duplication and irrelevant study types, 4,294 records proceeded to screening. Following the exclusion of 3,843 records based on titles and abstracts, 451 reports were assessed for eligibility. Out of these, 388 reports were excluded for specific reasons, leaving 63 studies for review.</alt-text>
</graphic>
</fig>
<p>As shown in <xref ref-type="table" rid="T1">
<bold>Table&#xa0;1</bold>
</xref>, 63 studies covering a total of 9,382 participants were included, with the sample sizes ranging from 40 to 938. The mean age of participants ranged from 51.42 to 74.97 years, the mean disease duration ranged from 0.56 to 9 years, and the mean age at onset ranged from 48.49 to 64.57 years. Regarding the use of scales for sleep quality in the PD patients, 58 studies used the PSQI, 2 studies used the PDSS, 2 studies used the PDSS-1 (the first entry in the Parkinson&#x2019;s Disease Sleep Scale), and 2 studies used the PDSS-2 (Parkinson&#x2019;s Disease Sleep Scale-2). We applied quality assessment on all 63 studies, where one was rated &#x201c;low quality&#x201d; (1.89%), while 62 studies were rated as &#x201c;moderate quality&#x201d; (98.41%), with study quality assessment scores ranging from 3 to 6 (See <xref ref-type="supplementary-material" rid="SF1">
<bold>Supplementary Table S1</bold>
</xref>).</p>
<table-wrap id="T1" position="float">
<label>Table&#xa0;1</label>
<caption>
<p>Characteristics of studies included in the meta-analysis.</p>
</caption>
<table frame="hsides">
<thead>
<tr>
<th valign="top" align="left">Author and Reference Number</th>
<th valign="top" align="left">Study site</th>
<th valign="top" align="left">Study design</th>
<th valign="top" align="left">Sample size</th>
<th valign="top" align="left">Scale</th>
<th valign="top" align="left">Cut-off</th>
<th valign="top" align="left">Mean age &#xb1; SD (Year)</th>
<th valign="top" align="left">Mean disease duration &#xb1; SD (Year)</th>
<th valign="top" align="left">Mean onset age &#xb1; SD (Year)</th>
<th valign="top" align="left">Diagnostic criteria</th>
<th valign="top" align="left">Mean MoCA total scores &#xb1; SD</th>
<th valign="top" align="left">Mean MMSE total scores &#xb1; SD</th>
<th valign="top" align="left">Mean UPDRS-3 scores &#xb1; SD</th>
<th valign="top" align="left">Mean LEDD &#xb1; SD (mg/d)</th>
<th valign="top" align="left">Mean H&amp;Y stage &#xb1; SD</th>
<th valign="top" align="left">Study quality score</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="center">Ma and Ren (<xref ref-type="bibr" rid="B76">76</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">110</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;4</td>
<td valign="top" align="center">63.2</td>
<td valign="top" align="center">4.1</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">21.22 &#xb1; 4.22</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">Chen, Zhang, Zhou, Yang and Feng (<xref ref-type="bibr" rid="B77">77</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">60</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;4</td>
<td valign="top" align="center">63.08 &#xb1; 11.93</td>
<td valign="top" align="center">6.33 &#xb1; 3.73</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Chen, Hu, Han, Zhang and Zhang (<xref ref-type="bibr" rid="B78">78</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">48</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">PD criteria by NEDC</td>
<td valign="top" align="center">26.54 &#xb1; 3.85</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">33.93 &#xb1; 19.82</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4.17</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Chen, Hong and Chen (<xref ref-type="bibr" rid="B79">79</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">265</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;7</td>
<td valign="top" align="center">63.1 &#xb1; 8.8</td>
<td valign="top" align="center">4.35 &#xb1; 2.12</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">24.53 &#xb1; 3.64</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">20.51 &#xb1; 10.01</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Guo, Yu, Zuo, Liu, Li, Pu, Hu, Lian, Wang, Yu, Jin, Zhu and Zhang (<xref ref-type="bibr" rid="B80">80</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">94</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;4</td>
<td valign="top" align="center">65.08 &#xb1; 2.23</td>
<td valign="top" align="center">5.15 &#xb1; 1.3</td>
<td valign="top" align="center">59.93 &#xb1; 2.01</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">21.58 &#xb1; 1.18</td>
<td valign="top" align="center">26.55 &#xb1; 0.94</td>
<td valign="top" align="center">19.09 &#xb1; 2.33</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Guo (<xref ref-type="bibr" rid="B81">81</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">100</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;7</td>
<td valign="top" align="center">74.97 &#xb1; 6.84</td>
<td valign="top" align="center">8.87 &#xb1; 4.3</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Yuan, Hu, Zhao, Wang, Zhang and Li (<xref ref-type="bibr" rid="B82">82</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">83</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;7</td>
<td valign="top" align="center">69.04 &#xb1; 9.69</td>
<td valign="top" align="center">5.05 &#xb1; 3.4</td>
<td valign="top" align="center">63.99 &#xb1; 9.69</td>
<td valign="top" align="center">Diagnostic criteria for PD in China</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">27.94 &#xb1; 18.17</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Xue (<xref ref-type="bibr" rid="B83">83</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">50</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;6</td>
<td valign="top" align="center">72.36 &#xb1; 5.69</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">Diagnostic criteria for PD in China</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Hu and Zhang (<xref ref-type="bibr" rid="B84">84</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">170</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;6</td>
<td valign="top" align="center">65.78 &#xb1; 9.1</td>
<td valign="top" align="center">4.08 &#xb1; 3.34</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">28.47 &#xb1; 1.64</td>
<td valign="top" align="center">16.3 &#xb1; 8.48</td>
<td valign="top" align="center">400 &#xb1; 210</td>
<td valign="top" align="center">2.12 &#xb1; 1.25</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Cheng, Yu and Wu (<xref ref-type="bibr" rid="B85">85</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">95</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;7</td>
<td valign="top" align="center">52.53 &#xb1; 14.71</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">Diagnostic criteria for PD in China</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Wang, Feng, Gu, Liu and Chen (<xref ref-type="bibr" rid="B86">86</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">486</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;6</td>
<td valign="top" align="center">62.52 &#xb1; 10.03</td>
<td valign="top" align="center">4.42 &#xb1; 3.69</td>
<td valign="top" align="center">58.18 &#xb1; 10.41</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">27.33 &#xb1; 2.89</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">Wang, Feng, Gu, Liu, Zhang and Chen (<xref ref-type="bibr" rid="B87">87</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">535</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;6</td>
<td valign="top" align="center">64.24 &#xb1; 8.05</td>
<td valign="top" align="center">4.39 &#xb1; 3.86</td>
<td valign="top" align="center">59.91 &#xb1; 8.76</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">27.17 &#xb1; 2.89</td>
<td valign="top" align="center">21.01 &#xb1; 12.27</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">2.04 &#xb1; 1.84</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">Wang and Wang (<xref ref-type="bibr" rid="B88">88</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">45</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;4</td>
<td valign="top" align="center">64.07 &#xb1; 10.1</td>
<td valign="top" align="center">2.66 &#xb1; 2.22</td>
<td valign="top" align="center">61.41 &#xb1; 10.18</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">22.66 &#xb1; 5.53</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">Wang, Sun, Ma, Shi, Li, Huang, Hu and Zheng (<xref ref-type="bibr" rid="B89">89</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">359</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;6</td>
<td valign="top" align="center">62.84 &#xb1; 7.81</td>
<td valign="top" align="center">6.25 &#xb1; 4.56</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">Diagnostic criteria for PD in China</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">38.19 &#xb1; 28.9</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Mao and Zhang (<xref ref-type="bibr" rid="B90">90</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">112</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;7</td>
<td valign="top" align="center">65.06 &#xb1; 6.49</td>
<td valign="top" align="center">6.39 &#xb1; 3.09</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">Diagnostic criteria for PD in China</td>
<td valign="top" align="center">21.83 &#xb1; 4.86</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">40.05 &#xb1; 14.21</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">1.67</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Mao, Dai and Liu (<xref ref-type="bibr" rid="B91">91</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">53</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">62.17 &#xb1; 9.26</td>
<td valign="top" align="center">4.91 &#xb1; 3.78</td>
<td valign="top" align="center">57.7 &#xb1; 8.43</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">1.8 &#xb1; 0.4</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Mao and Saimaiti (<xref ref-type="bibr" rid="B92">92</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">46</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">PD criteria by NEDC</td>
<td valign="top" align="center">28.11 &#xb1; 2.91</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">32.91 &#xb1; 16.13</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">3</td>
</tr>
<tr>
<td valign="top" align="center">Liang, Cui, Wu, Yu and Chen (<xref ref-type="bibr" rid="B93">93</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">120</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;6</td>
<td valign="top" align="center">62.73 &#xb1; 8.85</td>
<td valign="top" align="center">5.87 &#xb1; 2.87</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Zhu, Zheng and Yang (<xref ref-type="bibr" rid="B94">94</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">58</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">65.07 &#xb1; 8.1</td>
<td valign="top" align="center">5.26 &#xb1; 2.5</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">PD criteria by NEDC</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">1.6 &#xb1; 1.02</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">Cao, Liu, Ma, Chen, Ren, Zhang and Xu (<xref ref-type="bibr" rid="B95">95</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">75</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;6</td>
<td valign="top" align="center">63.2 &#xb1; 10.26</td>
<td valign="top" align="center">3.11 &#xb1; 2.92</td>
<td valign="top" align="center">58.24 &#xb1; 12.58</td>
<td valign="top" align="center">MDS-PD</td>
<td valign="top" align="center">19.53 &#xb1; 5.69</td>
<td valign="top" align="center">24.41 &#xb1; 4.80</td>
<td valign="top" align="center">31.93 &#xb1; 14.05</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">1.85 &#xb1; 1.20</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Cao, Yu, Su and Guo (<xref ref-type="bibr" rid="B96">96</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">93</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">67.58 &#xb1; 8.14</td>
<td valign="top" align="center">3.01 &#xb1; 2.74</td>
<td valign="top" align="center">64.57 &#xb1; 8.67</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">26.44 &#xb1; 1.03</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">2.47 &#xb1; 0.98</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Zhang, Gao and Wei (<xref ref-type="bibr" rid="B97">97</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">68</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;6</td>
<td valign="top" align="center">61.23 &#xb1; 7.1</td>
<td valign="top" align="center">3.78 &#xb1; 3.12</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Zhang, Zhang, Zhu, Jiang and Wu (<xref ref-type="bibr" rid="B98">98</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">253</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;6</td>
<td valign="top" align="center">68.84 &#xb1; 11.11</td>
<td valign="top" align="center">4.75 &#xb1; 4.2</td>
<td valign="top" align="center">63.95 &#xb1; 11.18</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">20.77 &#xb1; 5.02</td>
<td valign="top" align="center">25.31 &#xb1; 4.10</td>
<td valign="top" align="center">27.88&#xb1; 16.64</td>
<td valign="top" align="center">333.76 &#xb1; 327.31</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Zhang, Liu, Wang, Liu and Gu (<xref ref-type="bibr" rid="B99">99</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">127</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">66.38 &#xb1; 9.4</td>
<td valign="top" align="center">5.02 &#xb1; 3.6</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">MDS-PD</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">2.44 &#xb1; 0.52</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">Zhang, Luo and Liao (<xref ref-type="bibr" rid="B100">100</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">95</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;6</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">6.38 &#xb1; 4.38</td>
<td valign="top" align="center">61.51 &#xb1; 7.48</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">18.33 &#xb1; 3.40</td>
<td valign="top" align="center">20.75 &#xb1; 2.94</td>
<td valign="top" align="center">35.44 &#xb1; 17.05</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Cui, Qing, Liu and Chen (<xref ref-type="bibr" rid="B101">101</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">138</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;4</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">26.87 &#xb1; 1.83</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">song, Zhao, Li and Yin (<xref ref-type="bibr" rid="B102">102</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">40</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;7</td>
<td valign="top" align="center">63.85 &#xb1; 8.65</td>
<td valign="top" align="center">4.91 &#xb1; 3.51</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">Diagnostic criteria for PD in China</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">48.46 &#xb1; 23.25</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">2.84 &#xb1; 1.29</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Song, Sun, Ma, Lu, Fan, Wang, Wang and Wang (<xref ref-type="bibr" rid="B103">103</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">80</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">9 or above</td>
<td valign="top" align="center">66.82 &#xb1; 7.65</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">22.81 &#xb1; 4.19</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">Sun, Gao, Mo and Gong (<xref ref-type="bibr" rid="B104">104</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">56</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;6</td>
<td valign="top" align="center">55.77 &#xb1; 11.01</td>
<td valign="top" align="center">3.52 &#xb1; 2.86</td>
<td valign="top" align="center">51.86 &#xb1; 10.88</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">25.68 &#xb1; 13.96</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">1.94</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Lv, Wang, Zhu, Zhao and Guo (<xref ref-type="bibr" rid="B18">18</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">135</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;6</td>
<td valign="top" align="center">51.42 &#xb1; 14.63</td>
<td valign="top" align="center">2.35 &#xb1; 1.03</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">Diagnostic criteria for PD in China</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">18.91 &#xb1; 5.21</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">3.69 &#xb1; 0.53</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">Lu (<xref ref-type="bibr" rid="B105">105</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">70</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;7</td>
<td valign="top" align="center">64 &#xb1; 4</td>
<td valign="top" align="center">9 &#xb1; 4</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Liu and Chen (<xref ref-type="bibr" rid="B106">106</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">82</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">64.21 &#xb1; 11.24</td>
<td valign="top" align="center">3.24 &#xb1; 1.45</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">15.03 &#xb1; 8.61</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">1.85 &#xb1; 0.97</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Liu, Li, Fang, Qin and Wei (<xref ref-type="bibr" rid="B107">107</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">97</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;4</td>
<td valign="top" align="center">61.7 &#xb1; 9.2</td>
<td valign="top" align="center">2.1 &#xb1; 0.7</td>
<td valign="top" align="center">62.1 &#xb1; 9.7</td>
<td valign="top" align="center">PD criteria by NEDC</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">22.7 &#xb1; 8.9</td>
<td valign="top" align="center">432.3 &#xb1; 207.2</td>
<td valign="top" align="center">2.1 &#xb1; 0.6</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Liu, Chou, Ma, Zhang, Wang and Gu (<xref ref-type="bibr" rid="B108">108</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">71</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">66.5 &#xb1; 8.66</td>
<td valign="top" align="center">6.11 &#xb1; 4.05</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">22.03 &#xb1; 5.06</td>
<td valign="top" align="center">26.56 &#xb1; 3.10</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">2.4 &#xb1; 0.8</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">Liu, Wang, Wang, Mao and Wang (<xref ref-type="bibr" rid="B109">109</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">502</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;7</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">YU, PENG, LUO, HUANG and WANG (<xref ref-type="bibr" rid="B110">110</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">100</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;7</td>
<td valign="top" align="center">60.3 &#xb1; 8.26</td>
<td valign="top" align="center">4.24 &#xb1; 1.26</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">Diagnostic criteria for PD in China</td>
<td valign="top" align="center">21.89 &#xb1; 4.70</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Yi, Yu-Peng, Jiang-Ting, Jing-Yi, Qi-Xiong, Dan-Lei, Jing-Wei, Zhi-Juan, Yong-Jie, Zhe and Zheng (<xref ref-type="bibr" rid="B111">111</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">328</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">9 or above</td>
<td valign="top" align="center">60.5 &#xb1; 10.1</td>
<td valign="top" align="center">4.78 &#xb1; 4.27</td>
<td valign="top" align="center">55.53 &#xb1; 10.34</td>
<td valign="top" align="center">MDS-PD</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">25.19 &#xb1; 4.83</td>
<td valign="top" align="center">32.23 &#xb1; 17.30</td>
<td valign="top" align="center">575.78 &#xb1; 245.08</td>
<td valign="top" align="center">2.16 &#xb1; 0.99</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">Wang, Xiong, Chao, Zhuang, Li and Liu (<xref ref-type="bibr" rid="B112">112</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">938</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">Tang, Yang, Zhu, Gong, Sun, Chen, Guan, Yu, Wang, Zhang, Li, Ma and Wang (<xref ref-type="bibr" rid="B113">113</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">61</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">66.6 &#xb1; 6.10</td>
<td valign="top" align="center">4.5 &#xb1; 3.63</td>
<td valign="top" align="center">61.6 &#xb1; 7</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">26.38 &#xb1; 3.33</td>
<td valign="top" align="center">28.75 &#xb1; 2.22</td>
<td valign="top" align="center">22.63 &#xb1; 10</td>
<td valign="top" align="center">409.23 &#xb1; 249.56</td>
<td valign="top" align="center">2.45 &#xb1; 0.89</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">Song, Gu, An and Chan (<xref ref-type="bibr" rid="B114">114</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cohort</td>
<td valign="top" align="center">284</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Shulman, Taback, Bean and Weiner (<xref ref-type="bibr" rid="B115">115</xref>)</td>
<td valign="top" align="center">United States</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">99</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">67.4 &#xb1; 8</td>
<td valign="top" align="center">6.9 &#xb1; 5.7</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">22 &#xb1; 9</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">2.3 &#xb1; 0.8</td>
<td valign="top" align="center">6</td>
</tr>
<tr>
<td valign="top" align="center">Santos Garc&#xed;a, Cabo L&#xf3;pez, Labandeira Guerra, Y&#xe1;&#xf1;ez Ba&#xf1;a, Cimas Hernando, Paz Gonz&#xe1;lez, Alonso Losada, Gonzalez Palm&#xe1;s, Cores Bartolom&#xe9; and Mart&#xed;nez Mir&#xf3; (<xref ref-type="bibr" rid="B19">19</xref>)</td>
<td valign="top" align="center">Spain</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">47</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Sahebzadeh, Farsi Baf and Homam (<xref ref-type="bibr" rid="B116">116</xref>)</td>
<td valign="top" align="center">Iran</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">120</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">65.9 &#xb1; 11.7</td>
<td valign="top" align="center">2.6 &#xb1; 2.7</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">17.39 &#xb1; 5.20</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">6</td>
</tr>
<tr>
<td valign="top" align="center">Qiu, Gu, Liu and Li (<xref ref-type="bibr" rid="B117">117</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">101</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">9 or above</td>
<td valign="top" align="center">61.25 &#xb1; 7.83</td>
<td valign="top" align="center">7.82 &#xb1; 1.34</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">Diagnostic criteria for PD in China</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Qin, Li, Chen, Chen, Shi, Liu, Li, Xin and Gao (<xref ref-type="bibr" rid="B118">118</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">110</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;7</td>
<td valign="top" align="center">66.82 &#xb1; 8.23</td>
<td valign="top" align="center">3.67 &#xb1; 4.03</td>
<td valign="top" align="center">61.25 &#xb1; 10.38</td>
<td valign="top" align="center">MDS-PD</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">20.68 &#xb1; 18.02</td>
<td valign="top" align="center">447.32 &#xb1; 230.35</td>
<td valign="top" align="center">2.01 &#xb1; 0.87</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Pandey, Bajaj, Wadhwa and Anand (<xref ref-type="bibr" rid="B17">17</xref>)</td>
<td valign="top" align="center">India</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">100</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">59.2 &#xb1; 9.06</td>
<td valign="top" align="center">3.74 &#xb1; 3.67</td>
<td valign="top" align="center">55.5 &#xb1; 9.68</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">21.16 &#xb1; 6.98</td>
<td valign="top" align="center">367.53 &#xb1; 300.16</td>
<td valign="top" align="center">2.26 &#xb1; 0.64</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Mahale, Yadav and Pal (<xref ref-type="bibr" rid="B119">119</xref>)</td>
<td valign="top" align="center">India</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">156</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">52.47 &#xb1; 14.63</td>
<td valign="top" align="center">5.65 &#xb1; 4.64</td>
<td valign="top" align="center">48.49 &#xb1; 13.8</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">27.73 &#xb1; 2.21</td>
<td valign="top" align="center">28.81 &#xb1; 10.77</td>
<td valign="top" align="center">602.73 &#xb1; 353.30</td>
<td valign="top" align="center">2.23 &#xb1; 0.51</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Louter, van der Marck, Pevernagie, Munneke, Bloem and Overeem (<xref ref-type="bibr" rid="B120">120</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">153</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">65.9 &#xb1; 9.7</td>
<td valign="top" align="center">7.7 &#xb1; 5.7</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">468.4 &#xb1; 336.5</td>
<td valign="top" align="center">2.17</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Lin, Chen, Lu, Huang, Weng, Yeh, Lin and Hung (<xref ref-type="bibr" rid="B121">121</xref>)</td>
<td valign="top" align="center">Taiwan</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">225</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">65.7 &#xb1; 8.88</td>
<td valign="top" align="center">8.18 &#xb1; 5.2</td>
<td valign="top" align="center">57.5 &#xb1; 9.9</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">22.77 &#xb1; 10.8</td>
<td valign="top" align="center">425.84 &#xb1; 324.92</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">Havlikova, van Dijk, Nagyova, Rosenberger, Middel, Dubayova, Gdovinova and Groothoff (<xref ref-type="bibr" rid="B122">122</xref>)</td>
<td valign="top" align="center">Slovak Republic</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">93</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;4</td>
<td valign="top" align="center">68 &#xb1; 9.5</td>
<td valign="top" align="center">6.1 &#xb1; 5.9</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">15.88 &#xb1; 10.43</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">2 &#xb1; 1.2</td>
<td valign="top" align="center">5</td>
</tr>
<tr>
<td valign="top" align="center">Gao, Huang, Cai and Li (<xref ref-type="bibr" rid="B123">123</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">88</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">64.03 &#xb1; 10.5</td>
<td valign="top" align="center">5.41 &#xb1; 3.75</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">MDS-PD</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">25.59 &#xb1; 2.99</td>
<td valign="top" align="center">24.63 &#xb1; 7.58</td>
<td valign="top" align="center">510.85 &#xb1; 224.61</td>
<td valign="top" align="center">2.57 &#xb1; 1</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Duncan, Khoo, Yarnall, O&#x2019;Brien, Coleman, Brooks, Barker and Burn (<xref ref-type="bibr" rid="B124">124</xref>)</td>
<td valign="top" align="center">United Kingdom</td>
<td valign="top" align="center">cohort</td>
<td valign="top" align="center">158</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">66.5 &#xb1; 10.3</td>
<td valign="top" align="center">0.56 &#xb1; 0.49</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">25.1 &#xb1; 3.6</td>
<td valign="top" align="center">28.6 &#xb1; 1.4</td>
<td valign="top" align="center">27.1 &#xb1; 12</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">1.78</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Ding, Zhu, Lu, Shen, Dai and Zhu (<xref ref-type="bibr" rid="B125">125</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">75</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">9 or above</td>
<td valign="top" align="center">64.46 &#xb1; 6.46</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">PD criteria by NEDC</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">23.70 &#xb1; 3.81</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Shafazand, Wallace, Arheart, Vargas, Luca, Moore, Katzen, Levin and Singer (<xref ref-type="bibr" rid="B126">126</xref>)</td>
<td valign="top" align="center">United States</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">66</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;5</td>
<td valign="top" align="center">64.00 &#xb1; 10.00</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">363.20 &#xb1; 255.30</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Skorvanek, Nagyova, Rosenberger, Krokavcova, Saeedian, Groothoff, Gdovinova and van Dijk (<xref ref-type="bibr" rid="B127">127</xref>)</td>
<td valign="top" align="center">Slovensk&#xe1; republika</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">165</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;6</td>
<td valign="top" align="center">69.59 &#xb1; 8.56</td>
<td valign="top" align="center">6.93 &#xb1; 4.80</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">30.11 &#xb1; 13.62</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">2.41 &#xb1; 0.89</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Shi, Guan, Gao, Huang and Wang (<xref ref-type="bibr" rid="B128">128</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">120</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">9 or above</td>
<td valign="top" align="center">58.02 &#xb1; 8.56</td>
<td valign="top" align="center">5.48 &#xb1; 1.72</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">Diagnostic criteria for PD in China</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">27.94 &#xb1; 8.98</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">3.12 &#xb1; 1.22</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Dong and Tan (<xref ref-type="bibr" rid="B129">129</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">92</td>
<td valign="top" align="center">PSQI</td>
<td valign="top" align="center">&gt;7</td>
<td valign="top" align="center">69.77 &#xb1; 9.80</td>
<td valign="top" align="center">2.89 &#xb1; 4.00</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">Diagnostic criteria for PD in China</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">24.84 &#xb1; 18.67</td>
<td valign="top" align="center">333.70 &#xb1; 134.80</td>
<td valign="top" align="center">2.27 &#xb1; 0.74</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Chang, Fan, Chang and Wu (<xref ref-type="bibr" rid="B130">130</xref>)</td>
<td valign="top" align="center">Taiwan</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">134</td>
<td valign="top" align="center">PDSS-2</td>
<td valign="top" align="center">&gt;16</td>
<td valign="top" align="center">64.98 &#xb1; 9.19</td>
<td valign="top" align="center">7.86 &#xb1; 5.55</td>
<td valign="top" align="center">57.29 &#xb1; 10.66</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">27.44 &#xb1; 1.88</td>
<td valign="top" align="center">23.91 &#xb1; 11.92</td>
<td valign="top" align="center">647.39 &#xb1; 491.49</td>
<td valign="top" align="center">1.43 &#xb1; 0.64</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Shi (<xref ref-type="bibr" rid="B131">131</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">95</td>
<td valign="top" align="center">PDSS-2</td>
<td valign="top" align="center">&gt;12</td>
<td valign="top" align="center">67.81 &#xb1; 5.93</td>
<td valign="top" align="center">4.1 &#xb1; 0.71</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">Diagnostic criteria for PD in China</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Li, Yuan, Ye, Yuan, Gao and Hu (<xref ref-type="bibr" rid="B132">132</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">87</td>
<td valign="top" align="center">PDSS</td>
<td valign="top" align="center">&lt;91</td>
<td valign="top" align="center">66.99 &#xb1; 7.18</td>
<td valign="top" align="center">5.75 &#xb1; 3.94</td>
<td valign="top" align="center">61.77 &#xb1; 7.84</td>
<td valign="top" align="center">Diagnostic criteria for PD in China</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">27.58 &#xb1; 2.69</td>
<td valign="top" align="center">14.70 &#xb1; 5.25</td>
<td valign="top" align="center">490.78 &#xb1; 219.78</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Gui, Wang, Wu and Sun (<xref ref-type="bibr" rid="B133">133</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">178</td>
<td valign="top" align="center">PDSS</td>
<td valign="top" align="center">&lt;91</td>
<td valign="top" align="center">61.81 &#xb1; 10.92</td>
<td valign="top" align="center">4.50 &#xb1; 3.48</td>
<td valign="top" align="center">56.53 &#xb1; 10.98</td>
<td valign="top" align="center">UKPDS</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">26.61 &#xb1; 5.41</td>
<td valign="top" align="center">29.31 &#xb1; 14.66</td>
<td valign="top" align="center">441.26 &#xb1; 299.59</td>
<td valign="top" align="center">1.92 &#xb1; 0.75</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Hu, Sun, Lan, Wang, Li and Zhong (<xref ref-type="bibr" rid="B134">134</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">207</td>
<td valign="top" align="center">PDSS-1</td>
<td valign="top" align="center">&lt;6</td>
<td valign="top" align="center">61.29 &#xb1; 9.71</td>
<td valign="top" align="center">4.43 &#xb1; 4.74</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">PD criteria by NEDC</td>
<td valign="top" align="center">16.97 &#xb1; 6.18</td>
<td valign="top" align="center">23.50 &#xb1; 5.45</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">2.34 &#xb1; 0.85</td>
<td valign="top" align="center">4</td>
</tr>
<tr>
<td valign="top" align="center">Niu and Gou (<xref ref-type="bibr" rid="B135">135</xref>)</td>
<td valign="top" align="center">China</td>
<td valign="top" align="center">cross-sectional</td>
<td valign="top" align="center">131</td>
<td valign="top" align="center">PDSS-1</td>
<td valign="top" align="center">&lt;6</td>
<td valign="top" align="center">62.20 &#xb1; 8.00</td>
<td valign="top" align="center">2.27 &#xb1; 1.41</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">Diagnostic criteria for PD in China</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">NR</td>
<td valign="top" align="center">4</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn>
<p>NR, not reported; PSQI, Pittsburgh Sleep Quality Index; SD, standard deviation; H&amp;Y stage, Hoehn and Yahr stage; UKPDS, UK Parkinson&#x2019;s Disease Society Brain Bank Diagnostic Criteria; MDS-PD, Movement Disorder Society Clinical Diagnostic Criteria for Parkinson&#x2019;s disease; PD criteria by NEDC, Parkinson&#x2019;s diagnostic criteria established by Chinese Medical Association in the National Extrapyramidal Disorders Conference; MoCA, Montreal Cognitive Assessment; MMSE, Mini-Mental State Examination; UPDRS-3, The Unified Parkinson&#x2019;s Disease Rating Scale part 3 (Motor Examination); LEDD, Levodopa equivalent daily dose; PSQI, Pittsburgh Sleep Quality Index; PDSS, Parkinson&#x2019;s Disease Sleep Scale; PDSS-1, First item of Parkinson&#x2019;s Disease Sleep Scale; PDSS-2, Parkinson&#x2019;s disease sleep scale-2.</p>
</fn>
</table-wrap-foot>
</table-wrap>
</sec>
<sec id="s3_2">
<label>3.2</label>
<title>Pooled prevalence of poor sleep quality, PSQI global scores and PSQI component scores in Parkinson&#x2019;s disease patients</title>
<p>Based on the 63 studies, the pooled prevalence of poor sleep quality in PD patients was 58.07% (95% CI: 54.26&#x2013;61.88%) (<xref ref-type="fig" rid="f2">
<bold>Figure&#xa0;2</bold>
</xref>). As shown in <xref ref-type="table" rid="T2">
<bold>Table&#xa0;2</bold>
</xref>, 28 studies with 3,369 participants reported PSQI global scores among PD patients, with a pooled PSQI total score of 8.6 (95% CI: 7.66-9.55). The seven PSQI sleep component scores were reported in 6 studies (N=540). The pooled PSQI component scores ranged from 0.73 (95% CI: 0.31-1.16) for &#x201c;sleep medication use&#x201d; to 1.76 (95% CI: 1.38-2.14) for &#x201c;daytime dysfunction&#x201d; (see <xref ref-type="table" rid="T2">
<bold>Table&#xa0;2</bold>
</xref>).</p>
<fig id="f2" position="float">
<label>Figure&#xa0;2</label>
<caption>
<p>Forest plot of pooled prevalence of poor sleep quality in Parkinson&#x2019;s disease patients.</p>
</caption>
<graphic mimetype="image" mime-subtype="tiff" xlink:href="fpsyt-16-1606743-g002.tif">
<alt-text content-type="machine-generated">Forest plot showing prevalence estimates with 95% confidence intervals for various studies on events per 100 observations. Includes study names, events, and sample sizes. The random effects model at the bottom shows a pooled prevalence of 58.07 with a confidence interval of 54.26 to 61.88. Heterogeneity is high with an I&#xb2; of 94%.</alt-text>
</graphic>
</fig>
<table-wrap id="T2" position="float">
<label>Table&#xa0;2</label>
<caption>
<p>The pooled PSQI global and sleep component score in Parkinson&#x2019;s disease patients.</p>
</caption>
<table frame="hsides">
<thead>
<tr>
<th valign="middle" align="left">Variables</th>
<th valign="middle" align="left">Number of studies</th>
<th valign="middle" align="left">Sample size</th>
<th valign="middle" align="left">Pooled mean score (95% CI)</th>
<th valign="middle" align="left">
<italic>I</italic>2</th>
<th valign="middle" align="left">
<italic>P</italic> values</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="middle" align="left">PSQI global score</td>
<td valign="middle" align="center">28</td>
<td valign="middle" align="center">3369</td>
<td valign="middle" align="center">8.6101 (7.6664; 9.5538)</td>
<td valign="middle" align="center">98.80%</td>
<td valign="middle" align="center">&lt; 0.0001</td>
</tr>
<tr>
<td valign="middle" align="left">Subjective sleep quality</td>
<td valign="middle" align="center">6</td>
<td valign="middle" align="center">540</td>
<td valign="middle" align="center">1.3010 (0.9834; 1.6187)</td>
<td valign="middle" align="center">94.50%</td>
<td valign="middle" align="center">&lt; 0.0001</td>
</tr>
<tr>
<td valign="middle" align="left">Sleep latency</td>
<td valign="middle" align="center">6</td>
<td valign="middle" align="center">540</td>
<td valign="middle" align="center">1.3541 (0.9200; 1.7883)</td>
<td valign="middle" align="center">97.40%</td>
<td valign="middle" align="center">&lt; 0.0001</td>
</tr>
<tr>
<td valign="middle" align="left">Sleep duration</td>
<td valign="middle" align="center">6</td>
<td valign="middle" align="center">540</td>
<td valign="middle" align="center">1.1770 (0.9375; 1.4164)</td>
<td valign="middle" align="center">87.50%</td>
<td valign="middle" align="center">&lt; 0.0001</td>
</tr>
<tr>
<td valign="middle" align="left">Habitual sleep efficiency</td>
<td valign="middle" align="center">6</td>
<td valign="middle" align="center">540</td>
<td valign="middle" align="center">0.9736 (0.6394; 1.3078)</td>
<td valign="middle" align="center">93.30%</td>
<td valign="middle" align="center">&lt; 0.0001</td>
</tr>
<tr>
<td valign="middle" align="left">Sleep disturbance</td>
<td valign="middle" align="center">6</td>
<td valign="middle" align="center">540</td>
<td valign="middle" align="center">1.4194 (1.2180; 1.6208)</td>
<td valign="middle" align="center">91.80%</td>
<td valign="middle" align="center">&lt; 0.0001</td>
</tr>
<tr>
<td valign="middle" align="left">Use of sleep medications</td>
<td valign="middle" align="center">6</td>
<td valign="middle" align="center">540</td>
<td valign="middle" align="center">0.7347 (0.3085; 1.1609)</td>
<td valign="middle" align="center">98.40%</td>
<td valign="middle" align="center">&lt; 0.0001</td>
</tr>
<tr>
<td valign="middle" align="left">Daytime dysfunction</td>
<td valign="middle" align="center">6</td>
<td valign="middle" align="center">540</td>
<td valign="middle" align="center">1.7561 (1.3769; 2.1354)</td>
<td valign="middle" align="center">96.50%</td>
<td valign="middle" align="center">&lt; 0.0001</td>
</tr>
</tbody>
</table>
</table-wrap>
</sec>
<sec id="s3_3">
<label>3.3</label>
<title>Subgroup and meta-regression analyses</title>
<p>Subgroup analysis by comparing means showed that study site was significantly associated with the prevalence of poor sleep quality (p &lt; 0.01). Specifically, the highest prevalence of poor sleep quality in PD patients was reported in studies conducted in Europe &amp; Central Asia (59.65% 95%CI: 37.63-81.68%), while the lowest figure was reported in North America (47.88%, 95%CI: 40.26&#x2013;55.50%). There was also a significant subgroup difference in prevalence of poor sleep quality between countries by income (<italic>P &lt;</italic>0.01): the highest prevalence was reported in upper-middle income countries (58.37%, 95%CI: 54.35&#x2013;62.39%), while the lowest prevalence was reported in high income countries (56.40%, 95%CI: 40.51&#x2013;72.28%). There were significant subgroup differences between PD diagnostic criteria (P &lt; 0.01); the pooled prevalence of poor sleep quality was 59.04% (95% CI: 54.18-63.89%) in studies using the UK Parkinson&#x2019;s Disease Society Brain Bank Diagnostic Criteria (UKPDS), 59.11% (95% CI: 40.65-77.57%) in studies using the Movement Disorder Society Clinical Diagnostic Criteria for Parkinson&#x2019;s disease (MDS-PD), 57.20% (95% CI: 49.03-65.37%) in studies using the Diagnostic criteria of Chinese Parkinson&#x2019;s Disease &amp; Movement Disorders Society, Society for Neurology, Chinese Medical Association (Diagnostic criteria for PD in China) and 52.83% (95% CI: 42.44-63.22%) in studies using the diagnostic criteria for Parkinson&#x2019;s disease established by the National Extrapyramidal Disorders Conference (PD criteria by NEDC). Furthermore, the pooled prevalence rates of poor sleep quality were 60.57% (95% CI: 50.23-70.91%) in inpatients, 53.66% (95% CI: 45.21-62.11%) in outpatients, and 62.86% (95% CI: 53.72-72.00%) in the mixed group. Moreover, there were significant differences (p &lt; 0.01) between studies using different measures on sleep quality; the prevalence of poor sleep quality was 59.14% (95% CI: 55.19-63.09%) in studies using the PSQI, 40.96% (95% CI: 18.33-63.58%) in studies using the PDSS, 56.16% (95% CI: 22.69-89.62%) in studies using PDSS-1, and 47.16% (95% CI: 40.70-53.63%) in the studies using PDSS-2 (<xref ref-type="table" rid="T3">
<bold>Table&#xa0;3</bold>
</xref>). In meta-regression analyses, onset age (&#x3b2;=0.0132, z=2.0704, p=0.0384) was positively associated with the prevalence of poor sleep quality. However, mean age, illness duration, levodopa equivalent daily dose, and The Unified Parkinson&#x2019;s Disease Rating Scale part 3 (Motor Examination) score were not found to be statistically significant in the meta-regression (<xref ref-type="table" rid="T3">
<bold>Table&#xa0;3</bold>
</xref>).</p>
<table-wrap id="T3" position="float">
<label>Table&#xa0;3</label>
<caption>
<p>Subgroup analyses and meta-regression analyses.</p>
</caption>
<table frame="hsides">
<thead>
<tr>
<th valign="middle" colspan="13" align="left">Subgroup analysis</th>
</tr>
<tr>
<th valign="middle" colspan="2" align="left">Subgroups</th>
<th valign="middle" colspan="2" align="left">Categories</th>
<th valign="middle" colspan="2" align="left">No. of studies</th>
<th valign="middle" colspan="2" align="left">Prevalence (95%CI)</th>
<th valign="middle" align="left">
<italic>I<sup>2</sup>
</italic>
</th>
<th valign="middle" colspan="2" align="left">
<italic>P</italic>&#xa0;values within subgroups</th>
<th valign="middle" colspan="2" align="left">
<italic>P</italic>&#xa0;values across subgroups</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="middle" colspan="2" align="left" rowspan="4">Geographic region</td>
<td valign="middle" colspan="2" align="left">East Asia &amp; Pacific</td>
<td valign="middle" colspan="2" align="left">53</td>
<td valign="middle" colspan="2" align="left">58.37% (54.35-62.39%)</td>
<td valign="middle" align="left">94%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">Europe &amp; Central Asia</td>
<td valign="middle" colspan="2" align="left">5</td>
<td valign="middle" colspan="2" align="left">59.65% (37.61-81.68%)</td>
<td valign="middle" align="left">97%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">South Asia</td>
<td valign="middle" colspan="2" align="left">2</td>
<td valign="middle" colspan="2" align="left">48.04% (41.93-54.16%)</td>
<td valign="middle" align="left">0%</td>
<td valign="middle" colspan="2" align="left">0.62</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">North America</td>
<td valign="middle" colspan="2" align="left">2</td>
<td valign="middle" colspan="2" align="left">47.88% (40.26-55.50%)</td>
<td valign="middle" align="left">0%</td>
<td valign="middle" colspan="2" align="left">0.9</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
<tr>
<td valign="middle" colspan="2" align="left" rowspan="3">Countries by income</td>
<td valign="middle" colspan="2" align="left">Upper middle income</td>
<td valign="middle" colspan="2" align="left">53</td>
<td valign="middle" colspan="2" align="left">58.37% (54.35-62.39%)</td>
<td valign="middle" align="left">94%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">High income</td>
<td valign="middle" colspan="2" align="left">7</td>
<td valign="middle" colspan="2" align="left">56.40% (40.51-72.28%)</td>
<td valign="middle" align="left">96%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">Lower middle income</td>
<td valign="middle" colspan="2" align="left">3</td>
<td valign="middle" colspan="2" align="left">56.51% (40.51-72.51%)</td>
<td valign="middle" align="left">91%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
<tr>
<td valign="middle" colspan="2" align="left" rowspan="2">Study design</td>
<td valign="middle" colspan="2" align="left">Cross-sectional</td>
<td valign="middle" colspan="2" align="left">61</td>
<td valign="middle" colspan="2" align="left">58.24% (54.32-62.16%)</td>
<td valign="middle" align="left">94%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">Cohort</td>
<td valign="middle" colspan="2" align="left">2</td>
<td valign="middle" colspan="2" align="left">53.29% (41.23-65.35%)</td>
<td valign="middle" align="left">84%</td>
<td valign="middle" colspan="2" align="left">0.01</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
<tr>
<td valign="middle" colspan="2" align="left" rowspan="4">Diagnostic criteria</td>
<td valign="middle" colspan="2" align="left">UKPDS</td>
<td valign="middle" colspan="2" align="left">38</td>
<td valign="middle" colspan="2" align="left">59.04% (54.18-63.89%)</td>
<td valign="middle" align="left">94%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">MDS-PD</td>
<td valign="middle" colspan="2" align="left">5</td>
<td valign="middle" colspan="2" align="left">59.11% (40.65-77.57%)</td>
<td valign="middle" align="left">98%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">Diagnosticcriteria for PD in China</td>
<td valign="middle" colspan="2" align="left">14</td>
<td valign="middle" colspan="2" align="left">57.20% (49.03-65.37%)</td>
<td valign="middle" align="left">93%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">PD criteria by NEDC</td>
<td valign="middle" colspan="2" align="left">6</td>
<td valign="middle" colspan="2" align="left">52.83% (42.44-63.22%)</td>
<td valign="middle" align="left">83%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
<tr>
<td valign="middle" colspan="2" align="left" rowspan="2">Cut-off value*</td>
<td valign="middle" colspan="2" align="left">&gt;4, &gt;5, &gt;6 and</td>
<td valign="middle" colspan="2" align="left">41</td>
<td valign="middle" colspan="2" align="left">59.61% (54.87-64.35%)</td>
<td valign="middle" align="left">94%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">&gt;7 or above 7</td>
<td valign="middle" colspan="2" align="left">16</td>
<td valign="middle" colspan="2" align="left">57.93% (50.64-65.22%)</td>
<td valign="middle" align="left">95%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
<tr>
<td valign="middle" colspan="2" align="left" rowspan="3">Patient source</td>
<td valign="middle" colspan="2" align="left">Mixed</td>
<td valign="middle" colspan="2" align="left">15</td>
<td valign="middle" colspan="2" align="left">62.86% (53.72-72.00%)</td>
<td valign="middle" align="left">95%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">Inpatients</td>
<td valign="middle" colspan="2" align="left">3</td>
<td valign="middle" colspan="2" align="left">60.57% (50.23-70.91%)</td>
<td valign="middle" align="left">77%</td>
<td valign="middle" colspan="2" align="left">0.01</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">Outpatients</td>
<td valign="middle" colspan="2" align="left">12</td>
<td valign="middle" colspan="2" align="left">53.66% (45.21-62.11%)</td>
<td valign="middle" align="left">96%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
<tr>
<td valign="middle" colspan="2" align="left" rowspan="4">Scale</td>
<td valign="middle" colspan="2" align="left">PSQI</td>
<td valign="middle" colspan="2" align="left">57</td>
<td valign="middle" colspan="2" align="left">59.14% (55.19-63.09%)</td>
<td valign="middle" align="left">94%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">PDSS</td>
<td valign="middle" colspan="2" align="left">2</td>
<td valign="middle" colspan="2" align="left">40.96% (18.33-63.58%)</td>
<td valign="middle" align="left">92%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">PDSS-1</td>
<td valign="middle" colspan="2" align="left">2</td>
<td valign="middle" colspan="2" align="left">56.16% (22.69-89.62%)</td>
<td valign="middle" align="left">98%</td>
<td valign="middle" colspan="2" align="left">&lt;0.01</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
<tr>
<td valign="middle" colspan="2" align="left">PDSS-2</td>
<td valign="middle" colspan="2" align="left">2</td>
<td valign="middle" colspan="2" align="left">47.16% (40.70-53.63%)</td>
<td valign="middle" align="left">0%</td>
<td valign="middle" colspan="2" align="left">0.83</td>
<td valign="middle" colspan="2" align="left"/>
</tr>
</tbody>
</table>
<table frame="hsides">
<thead>
<tr>
<th valign="middle" colspan="8" align="left">Meta-regression analyses</th>
</tr>
<tr>
<th valign="middle" align="left">Variables</th>
<th valign="middle" align="left">Number of studies</th>
<th valign="middle" align="left">Coefficient</th>
<th valign="middle" align="left">Standard Error</th>
<th valign="middle" align="left">95% Lower</th>
<th valign="middle" align="left">95% Upper</th>
<th valign="middle" align="left">z values</th>
<th valign="middle" align="left">P values</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="middle" align="left">Mean age</td>
<td valign="middle" align="right">55</td>
<td valign="middle" align="right">0.0076</td>
<td valign="middle" align="right">0.0048</td>
<td valign="middle" align="right">-0.0017</td>
<td valign="middle" align="right">0.0169</td>
<td valign="middle" align="right">1.5949</td>
<td valign="middle" align="right">0.1107</td>
</tr>
<tr>
<td valign="middle" align="left">Illness duration</td>
<td valign="middle" align="right">51</td>
<td valign="middle" align="right">0.0105</td>
<td valign="middle" align="right">0.0124</td>
<td valign="middle" align="right">-0.0139</td>
<td valign="middle" align="right">0.0348</td>
<td valign="middle" align="right">0.8415</td>
<td valign="middle" align="right">0.4001</td>
</tr>
<tr>
<td valign="middle" align="left">Male proportion</td>
<td valign="middle" align="right">59</td>
<td valign="middle" align="right">-0.1265</td>
<td valign="middle" align="right">0.2418</td>
<td valign="middle" align="right">-0.6005</td>
<td valign="middle" align="right">0.3474</td>
<td valign="middle" align="right">-0.5233</td>
<td valign="middle" align="right">0.6008</td>
</tr>
<tr>
<td valign="middle" align="left">Onset age</td>
<td valign="middle" align="right">21</td>
<td valign="middle" align="right">0.0132</td>
<td valign="middle" align="right">0.0064</td>
<td valign="middle" align="right">0.0007</td>
<td valign="middle" align="right">0.0258</td>
<td valign="middle" align="right">2.0704</td>
<td valign="middle" align="right">
<bold>0.0384</bold>
</td>
</tr>
<tr>
<td valign="middle" align="left">MoCA</td>
<td valign="middle" align="right">16</td>
<td valign="middle" align="right">-0.0047</td>
<td valign="middle" align="right">0.0115</td>
<td valign="middle" align="right">-0.0272</td>
<td valign="middle" align="right">0.0178</td>
<td valign="middle" align="right">-0.4075</td>
<td valign="middle" align="right">0.6836</td>
</tr>
<tr>
<td valign="middle" align="left">MMSE</td>
<td valign="middle" align="right">19</td>
<td valign="middle" align="right">-0.0044</td>
<td valign="middle" align="right">0.0073</td>
<td valign="middle" align="right">-0.0186</td>
<td valign="middle" align="right">0.0099</td>
<td valign="middle" align="right">-0.6044</td>
<td valign="middle" align="right">0.5456</td>
</tr>
<tr>
<td valign="middle" align="left">UPDRS-3</td>
<td valign="middle" align="right">33</td>
<td valign="middle" align="right">0.0068</td>
<td valign="middle" align="right">0.0043</td>
<td valign="middle" align="right">-0.0017</td>
<td valign="middle" align="right">0.0153</td>
<td valign="middle" align="right">1.5580</td>
<td valign="middle" align="right">0.1192</td>
</tr>
<tr>
<td valign="middle" align="left">LEDD mean</td>
<td valign="middle" align="right">16</td>
<td valign="middle" align="right">-0.0006</td>
<td valign="middle" align="right">0.0004</td>
<td valign="middle" align="right">-0.0014</td>
<td valign="middle" align="right">0.0002</td>
<td valign="middle" align="right">-1.5178</td>
<td valign="middle" align="right">0.1291</td>
</tr>
<tr>
<td valign="middle" align="left">H&amp;YStage</td>
<td valign="middle" align="right">31</td>
<td valign="middle" align="right">-0.0126</td>
<td valign="middle" align="right">0.0547</td>
<td valign="middle" align="right">-0.1198</td>
<td valign="middle" align="right">0.0946</td>
<td valign="middle" align="right">-0.2304</td>
<td valign="middle" align="right">0.8178</td>
</tr>
<tr>
<td valign="middle" align="left">Study quality</td>
<td valign="middle" align="right">63</td>
<td valign="middle" align="right">-0.0682</td>
<td valign="middle" align="right">0.0348</td>
<td valign="middle" align="right">-0.1363</td>
<td valign="middle" align="right">-0.0001</td>
<td valign="middle" align="right">-1.9618</td>
<td valign="middle" align="right">
<bold>0.0498</bold>
</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn>
<p>*Only the study using the PSQI;H&amp;Y stage: Hoehn and Yahr stage; UKPDS, UK Parkinson&#x2019;s Disease Society Brain Bank Diagnostic Criteria; MDS-PD, Movement Disorder Society Clinical Diagnostic Criteria for Parkinson&#x2019;s disease; PD criteria by NEDC, Parkinson&#x2019;s diagnostic criteria established by the National Extrapyramidal Disorders Conference; MoCA, Montreal Cognitive Assessment; MMSE, Mini-Mental State Examination; UPDRS-3, The Unified Parkinson&#x2019;s Disease Rating Scale part 3 (Motor Examination); H&amp;Y stage, Hoehn and Yahr stage; LEDD, Levodopa equivalent daily dose; PSQI, Pittsburgh Sleep Quality Index; PDSS, Parkinson&#x2019;s Disease Sleep Scale; PDSS-1, First item of Parkinson&#x2019;s Disease Sleep Scale; PDSS-2, Parkinson&#x2019;s disease sleep scale-2.</p>
</fn>
</table-wrap-foot>
</table-wrap>
</sec>
<sec id="s3_4">
<label>3.4</label>
<title>Publication bias and sensitivity analyses</title>
<p>The funnel plot assessment and Egger&#x2019;s test value suggested no significant publication bias (Egger&#x2019;s test t = 1.42, P= 0.1608) (See <xref ref-type="supplementary-material" rid="SF2">
<bold>Supplementary Figure S1</bold>
</xref>). Sensitivity analyses did not identify any outlying studies that could significantly change primary results (See <xref ref-type="supplementary-material" rid="SF3">
<bold>Supplementary Figure S2</bold>
</xref>). To avoid selection bias, no studies were excluded based solely on quality assessment. Sensitivity analysis confirmed that low-quality studies did not significantly alter the pooled prevalence estimates.</p>
</sec>
</sec>
<sec id="s4" sec-type="discussion">
<label>4</label>
<title>Discussion</title>
<p>To the best of our knowledge, this was the first systematic review and meta-analysis to examine the prevalence of poor sleep quality in patients with PD. Based on 63 studies, comprising 9,382 PD patients, the prevalence of poor sleep quality in patients with PD was 58.07% (95% CI: 54.26-61.88%). The factors associated with the prevalence of poor sleep quality included study region, income, diagnostic criteria, patient source and PD age of onset.</p>
<p>The pooled PSQI global score in this study was 8.61 (95% CI: 7.67-9.55), which was higher than the findings reported in most other population studies. For example, the global PSQI scores in a general population sample were 3.18 &#xb1; 2.28 in Japan (<xref ref-type="bibr" rid="B35">35</xref>), 5.00 &#xb1; 3.37 in Germany (<xref ref-type="bibr" rid="B36">36</xref>), 5.14 &#xb1; 3.90 in Spain (<xref ref-type="bibr" rid="B37">37</xref>), and 5.5 &#xb1; 2.8 in Singapore (<xref ref-type="bibr" rid="B38">38</xref>). The overall prevalence of poor sleep quality in PD patients was 58.07% (95% CI: 54.26-61.88%), which is substantially higher than most figures reported in other populations, including Singaporean working population (42.5%; 95% CI: 37.9-47.1%) (<xref ref-type="bibr" rid="B38">38</xref>), Chinese elderly population (35.9%; 95% CI: 30.6%-41.2%) (<xref ref-type="bibr" rid="B39">39</xref>), perinatal and postpartum women (54.2%; 95% CI: 47.9-60.5%) (<xref ref-type="bibr" rid="B24">24</xref>), medical students (55%; 95% CI 48.0%-62.0%) (<xref ref-type="bibr" rid="B40">40</xref>), patients with tinnitus (53.5%; 95% CI: 40.2-66.8%) (<xref ref-type="bibr" rid="B41">41</xref>), and patients with irritable bowel syndrome (37.6%; 95% CI: 31.4-44.3%) (<xref ref-type="bibr" rid="B42">42</xref>).</p>
<p>The high prevalence of poor sleep quality in PD patients may be attributed to the disease characteristics. Degenerative changes in the brain associated with the disease can directly impact sleep/wake mechanisms, leading to sleep disruptions (<xref ref-type="bibr" rid="B43">43</xref>). Additionally, movement difficulties, such as the inability to move around in bed, involuntary movements, dystonia, and pain caused by leg spasms, all of which can interfere with sleep maintenance (<xref ref-type="bibr" rid="B44">44</xref>). However, the overall prevalence of poor sleep quality in PD patients is lower than the rates reported in patients with chronic non-cancer pain (75.3%, 95% CI: 62.8-87.8%) (<xref ref-type="bibr" rid="B45">45</xref>), and hemodialysis patients (75.30%, 95% CI: 70.08-82.50%) (<xref ref-type="bibr" rid="B46">46</xref>). The prevalence is also lower than that in certain occupational groups with high work demands, such as nurses (61.00%, 95% CI: 55.8-66.1%) (<xref ref-type="bibr" rid="B47">47</xref>) and military personnel (69.00%, 95% CI: 62.33-75.30%) (<xref ref-type="bibr" rid="B25">25</xref>), who often experience high stress, shift work, long work hours, high burnout, and exposure to trauma (<xref ref-type="bibr" rid="B48">48</xref>).</p>
<p>In subgroup analyses, we found that the overall prevalence of poor sleep quality in PD patients was significantly lower in North America (47.88%, 95% CI: 40.26-55.50%) and high-income countries (56.40%, 95% CI: 40.51-72.28%) compared to other regions and countries. The burden of PD appears to be greater in low-income areas, which may contribute to poorer sleep quality (<xref ref-type="bibr" rid="B49">49</xref>, <xref ref-type="bibr" rid="B50">50</xref>). On the other hand, higher-income countries may have access to better healthcare facilities, resources, and support, which can indirectly lower the risk of poor sleep quality PD patients (<xref ref-type="bibr" rid="B51">51</xref>). Greater healthcare resources in high-income countries may lead to more effective management of symptoms in PD patients in these countries, and thereby improving their sleep quality.</p>
<p>The overall prevalence of poor sleep quality was significantly higher among inpatients (60.57%, 95% CI: 50.23-70.91%) compared to outpatients (53.66%, 95% CI: 45.21-62.11%), which may be attributed to the severity of PD. Hospitalized patients usually suffer from a more advanced stage of the disease, necessitating closer medical monitoring and treatment (<xref ref-type="bibr" rid="B52">52</xref>). Certain symptoms, such as tremors, muscle stiffness, and difficulties with motor control, can all contribute to disrupted sleep (<xref ref-type="bibr" rid="B53">53</xref>, <xref ref-type="bibr" rid="B54">54</xref>). Furthermore, changes in the environment such as being hospitalized or separated from their families and regular living environment can also contribute to a decline in sleep quality (<xref ref-type="bibr" rid="B55">55</xref>, <xref ref-type="bibr" rid="B56">56</xref>). Consequently, hospitalized PD patients are more likely to encounter sleep problems.</p>
<p>In the subgroup analyses, the pooled prevalence of poor sleep quality in studies using the MDS-PD (59.11%, 95% CI: 40.65-77.57%) was significantly higher than those using the diagnostic PD criteria by NEDC (52.83%, 95% CI: 42.44-63.22%). Notably, certain studies had applied the UK Parkinson&#x2019;s Disease Society Brain Bank (UKPDS) criteria and the Parkinson&#x2019;s diagnostic criteria established by Chinese Medical Association (CMA) in the National Extrapyramidal Disorders Conference (NEDC), both of which differ from the Movement Disorder Society Clinical Diagnostic Criteria for Parkinson&#x2019;s disease(MDS-PD) in terms of diagnostic strictness and clinical application. Such diagnostic variations represent a key source of heterogeneity: the MDS-PD incorporates advanced biomarkers and updated clinical features to maximize specificity (<xref ref-type="bibr" rid="B23">23</xref>), whereas the UKPDS relies primarily on classic motor symptoms with established high sensitivity but lower specificity for early PD. The CMA guidelines adapt international standards to regional practices, potentially introducing operational variability, and NEDC (1984) lacks contemporary validation with possible under-identification of non-motor phenotypes (<xref ref-type="bibr" rid="B57">57</xref>, <xref ref-type="bibr" rid="B58">58</xref>). Such methodological heterogeneity can directly influence prevalence estimates, as stricter criteria (e.g., MDS-PD) may capture patients with more advanced pathology and higher comorbidity burden, while broader criteria (e.g., NEDC/UKPDS) can include borderline cases with milder sleep disturbances. Consequently, the observed prevalence differences likely reflect both true biological variability and diagnostic threshold effects, necessitating cautious interpretation of cross-criteria study comparisons.</p>
<p>Subgroup analyses also revealed significantly higher pooled prevalence rates in cross-sectional studies (58.24%, 95% CI: 54.32-62.16%) compared to cohort studies (53.29%, 95% CI: 41.23-65.35%). It should be noted that only a small number of cohort studies (n = 2) were included, which might have resulted in less reliable estimates. Similarly, the higher prevalence observed in studies using the PSQI might partially reflect selection bias, due to the small number of studies using the PDSS (n = 2), PDSS-1 (n = 2), and PDSS-2 (n=2). Therefore, the findings of these subgroup analysis are tentative.</p>
<p>In meta-regression analyses, the age of onset of PD was positively associated with prevalence of poor sleep quality. Previous studies found that gender and age of onset are significant factors influencing the clinical phenotype of PD, affecting both motor symptoms and various non-motor symptoms (<xref ref-type="bibr" rid="B59">59</xref>). Patients with late-onset PD tend to experience more frequent non-motor symptoms, including cognitive dysfunction, autonomic dysfunction, and sleep disturbances (<xref ref-type="bibr" rid="B60">60</xref>, <xref ref-type="bibr" rid="B61">61</xref>). A study conducted in China on non-motor symptoms in PD found positive correlations between age, daily levodopa dose, and Non-Motor Symptoms Scale (NMSS) scores in patients with late-onset PD. However, these correlations were not observed in those with early-onset PD, suggesting that age and daily levodopa dose may play a more significant role in the severity of non-motor symptoms in patients with late-onset PD compared to those with early-onset PD (<xref ref-type="bibr" rid="B62">62</xref>). Several brainstem nuclei are potentially involved in the mechanisms underlying non-motor symptoms such as gastrointestinal regulation, pain perception, emotion control, and sleep-wake cycles (<xref ref-type="bibr" rid="B63">63</xref>, <xref ref-type="bibr" rid="B64">64</xref>). The presence of Lewy bodies, which are composed of abnormal &#x3b1;-synuclein and are found outside the dopaminergic neurons of the midbrain, probably contribute to the pathology of non-motor manifestations in PD (<xref ref-type="bibr" rid="B63">63</xref>, <xref ref-type="bibr" rid="B65">65</xref>, <xref ref-type="bibr" rid="B66">66</xref>). Different distribution and severity of central nervous system lesions and pathophysiological course of PD between patients with early-onset and late-onset PD may be crucial factors influencing the non-motor features (e.g., sleep quality) associated with the disease (<xref ref-type="bibr" rid="B62">62</xref>).</p>
<p>Overall, our meta-analysis indicates that patients with PD have a high prevalence of poor sleep quality. Sleep problems are closely associated with mental health (<xref ref-type="bibr" rid="B67">67</xref>), and patients with PD often experience psychological stress (<xref ref-type="bibr" rid="B68">68</xref>), anxiety and depression (<xref ref-type="bibr" rid="B69">69</xref>, <xref ref-type="bibr" rid="B70">70</xref>). Therefore, maintaining good sleep quality plays a crucial role in sustaining emotional and mental stability and enhancing the mental well-being and quality of life for patients (<xref ref-type="bibr" rid="B71">71</xref>). Cognitive decline and difficulties with concentration are common challenges faced by PD patients (<xref ref-type="bibr" rid="B72">72</xref>, <xref ref-type="bibr" rid="B73">73</xref>). Prioritizing sleep quality in patients with PD is essential for managing symptoms, enhancing mental health, and preserving cognitive functioning. By optimizing the sleep environment, establishing healthy sleep habits, and utilizing medications or other treatments, when necessary, the sleep quality of patients with PD can be improved. Moreover, meta-regression showed that study quality was negatively associated with sleep quality in PD patients. Thus, lower study quality may lead to underestimation of sleep problems in PD patients. Improving the methodological rigor of studies may help to more accurately assess the severity of sleep quality problems (<xref ref-type="bibr" rid="B74">74</xref>).</p>
<p>Strengths of this meta-analysis include high number of included studies and large sample size, and the utilization of comprehensive analytical methods, such as subgroup and meta-regression analyses, to identify factors associated with poor sleep quality. Nonetheless, several limitations should be noted. First, despite use of sophisticated statistical methods, heterogeneity still remained in the subgroup analyses, as is expected in meta-analyses of epidemiological surveys, as pointed out in previous studies (<xref ref-type="bibr" rid="B25">25</xref>, <xref ref-type="bibr" rid="B47">47</xref>). Second, certain factors related to poor sleep quality, such as living environment, psychiatric comorbidities, and educational background, were not included in most studies. Third, wide confidence intervals for subgroups might be related to small sample sizes or the use of different PD diagnostic criteria in some studies. Fourth, the overrepresentation of Chinese studies might introduce bias that could affect the generalizability of the findings to other populations (<xref ref-type="bibr" rid="B75">75</xref>). Fifth, while our analysis identified key correlates of poor sleep quality, the preponderance of cross-sectional data precluded any causal conclusions. Longitudinal studies are warranted to explore the temporal relationships, particularly between sleep deterioration and PD progression trajectories. Furthermore, significant heterogeneity in PD diagnostic criteria (e.g., MDS-PD vs. UKPDS vs. CMA vs. NEDC) could result in methodological variability. Although this reflects real-world clinical practice, differences in diagnostic sensitivity/specificity might influence pooled prevalence estimates and subgroup comparability. Future meta-analyses would benefit from standardized application of contemporary diagnostic frameworks of PD.</p>
<p>In conclusion, poor sleep quality is common among patients with PD, particularly in lower middle-income countries and Europe &amp; Central Asia regions. To mitigate the adverse effects of poor sleep quality in PD patients, regular monitoring of sleep quality and sleep hygiene is crucial, particularly in high-risk subgroups. Additionally, further studies of sleep quality and PD patients in low- and middle-income countries are warranted, as well as prospective cohort studies to clarify the causality between poor sleep quality and other factors.</p>
</sec>
</body>
<back>
<sec id="s5" sec-type="data-availability">
<title>Data availability statement</title>
<p>The original contributions presented in the study are included in the article/<xref ref-type="supplementary-material" rid="SF1">
<bold>Supplementary Material</bold>
</xref>. Further inquiries can be directed to the corresponding authors.</p>
</sec>
<sec id="s6" sec-type="author-contributions">
<title>Author contributions</title>
<p>TS: Conceptualization, Data curation, Formal Analysis, Methodology, Writing &#x2013; original draft, Writing &#x2013; review &amp; editing. YW: Data curation, Formal Analysis, Methodology, Writing &#x2013; review &amp; editing. JL: Data curation, Formal Analysis, Methodology, Writing &#x2013; review &amp; editing. WB: Data curation, Formal Analysis, Methodology, Writing &#x2013; review &amp; editing. HS: Writing &#x2013; review &amp; editing. SR: Data curation, Writing &#x2013; review &amp; editing. HZ: Data curation, Writing &#x2013; review &amp; editing. GU: Writing &#x2013; review &amp; editing. ZS: Data curation, Writing &#x2013; review &amp; editing. TC: Data curation, Writing &#x2013; review &amp; editing. CN: Conceptualization, Writing &#x2013; review &amp; editing. YX: Conceptualization, Writing &#x2013; original draft, Writing &#x2013; review &amp; editing. GW: Data curation, Methodology, Writing &#x2013; review &amp; editing.</p>
</sec>
<sec id="s7" sec-type="funding-information">
<title>Funding</title>
<p>The author(s) declare that financial support was received for the research and/or publication of this article. The study was supported by Beijing High Level Public Health Technology Talent Construction Project (Discipline Backbone-01-028), the Beijing Municipal Science &amp; Technology Commission (No. Z181100001518005), and the Beijing Hospitals Authority Clinical Medicine Development of Special Funding Support (XMLX202128) and the University of Macau (MYRG2019-00066-FHS; MYRG2022-00187-FHS).</p>
</sec>
<ack>
<title>Acknowledgments</title>
<p>The authors are grateful to all participants and clinicians involved in this study.</p>
</ack>
<sec id="s8" sec-type="COI-statement">
<title>Conflict of interest</title>
<p>The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p>
</sec>
<sec id="s9" sec-type="ai-statement">
<title>Generative AI statement</title>
<p>The author(s) declare that no Generative AI was used in the creation of this manuscript.</p>
</sec>
<sec id="s10" sec-type="disclaimer">
<title>Publisher&#x2019;s note</title>
<p>All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.</p>
</sec>
<sec id="s11" sec-type="supplementary-material">
<title>Supplementary material</title>
<p>The Supplementary Material for this article can be found online at: <ext-link ext-link-type="uri" xlink:href="https://www.frontiersin.org/articles/10.3389/fpsyt.2025.1606743/full#supplementary-material">https://www.frontiersin.org/articles/10.3389/fpsyt.2025.1606743/full#supplementary-material</ext-link>
</p>
<supplementary-material xlink:href="SupplementaryFile1.docx" id="SF1" mimetype="application/vnd.openxmlformats-officedocument.wordprocessingml.document">
<label>Supplementary Table&#xa0;1</label>
<caption>
<p>Quality assessment of included studies.</p>
</caption>
</supplementary-material>
<supplementary-material xlink:href="SupplementaryFile1.docx" id="SF2" mimetype="application/vnd.openxmlformats-officedocument.wordprocessingml.document">
<label>Supplementary Figure&#xa0;1</label>
<caption>
<p>Funnel plot of pooled prevalence of poor sleep quality in Parkinson&#x2019;s disease patients.</p>
</caption>
</supplementary-material>
<supplementary-material xlink:href="SupplementaryFile1.docx" id="SF3" mimetype="application/vnd.openxmlformats-officedocument.wordprocessingml.document">
<label>Supplementary Figure&#xa0;2</label>
<caption>
<p>Sensitivity analysis of pooled prevalence of poor sleep quality in Parkinson&#x2019;s disease patients.</p>
</caption>
</supplementary-material>
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