The Web of Science (WoS), an authoritative database that could provide the overall data source, was widely used for search data. In this study, data were obtained from the Science Citation Index Expanded (SCI-E) database within the “Web of Science Core Collection” (WoSCC) between 1 January 2013 and 24 April 2023. The search strategy was: TI = (“MCI*” OR “Mild Cognitive Impairment*” OR “Mild Neurocognitive Disorder*” OR “Mild cognitive*” OR “Mild Cognitive dysfunction*”) AND Language = (“English”) AND Document Type = (“Article”). After manually reading the titles and abstracts, irrelevant documents were excluded, and a total of 6,075 documents finally met the inclusion criteria and were included. Then the data was imported into the CiteSpace software for checking duplicates. To get comprehensive information, we use the mode “Full Record and Cited References.” These retrieved records were saved as “plain text” file formats and named download_txt. All data collection was conducted on 24 April 2023. In addition, Citations, Impact factor (IF), and H-index were used to supplement. Figure 1 depicts the flow chart of the literature screening.

The full data was analyzed using CiteSpace 6.2.4 and VOSviewer software 1.6.19. VOSviewer 1.6.19 was used for institutions, authors, and co-cited authors, journals, and Keyword analyses. CiteSpace 6.2.4 was used for presentation visualization analysis of journals, co-cited references, and keywords. SCImago Graphica 1.0.36 was used for performing the cooperative relations between countries/regions. Bibliometrix R Package software 4.3.0 was used to display source dynamics and topic dynamics.

The basic parameters of CiteSpace were set as follows: (1) time slicing (2013–2023), year per slice for 1 year; (2) for the text processing section, set the term source to Title, Abstract, Author, and Keywords; (3) node type was selected at a time. The parameters of VOSviewer were set as below: (1) set the analysis type to co-occurrence; (2) the counting method was set as full counting; (3) according to data analysis requirements, select different visualization maps such as network, overlay, and density visualization.

According to the Citation Report of WoS, the total citation number of the 6,075 documents was 123,493, with an average of 20.33 citations per article, and the H-index of was 116. During the past decade, dynamic change in the annual global publications shows a two-stage trend (Figure 2). Stage 1: during the period from 2013 to 2018, the annual publication volume fluctuated steadily between 410 and 530, and the number of publications each year was relatively stable. Stage 2: during the period from 2018 to 2022, the number of papers published each year has greatly increased, with an average annual increase of about 100 articles. The overall upward trend of citation number, increasing frequency of publications, and high H-index show that scholars pay more and more attention to the field of mild cognitive impairment.

There are 95 countries involved in the study of mild cognitive impairment. As the two most prolific countries, the United States in North America topped the list with 1,739 publications, followed by China in Asia with 1,479 publications. These two countries alone account for half of all global publications. Otherwise, productive countries are mostly concentrated in Europe (Figure 3A).

The circles in Figure 3B represent countries/regions, and their size correlates with the volume of publications. The color of the line is related to the strength of cooperation, with red representing the country/region’s important position in the network of international cooperation. As is shown in the chart, the United States ranks first in terms of production and cooperation intensity. Although Italy (538 articles) and Germany (372 articles) do not rank very high in terms of output, they rank second and third, respectively, in terms of international partnerships. China ranked second in the number of articles published, but 10th in international cooperation (Table 1). This may be related to the geographical location and the complex flow of research.

The H-index is one of the indicators to evaluate influence. The United States ranks first with the 94 H-index. There is little difference in the H-index among China, the United Kingdom, and Italy, ranking second, third, and fourth, respectively. Germany, the United Kingdom, and the United States rank among the top three in terms of average citations per paper, while China ranked 10th with 14.31. This shows that the Occident has a higher influence.

A total of 6,198 institutions worldwide have contributed to this field over the past 10 years, of which the University of California System ranks first in the high-yield list with 277 publications. Among the top ten most productive institutions, six belong to the United States, which shows the amazing academic dominance of the United States in this field. The institution’s average citations per article of 56 far exceeds the second place, but it ranks second on the H-index list, which may be due to the small number of articles published (Table 2). The purple outer circle of the node in Figure 4 represents high centrality, as shown in the figure, most of the highly centralized countries are located in Europe and America, especially in the United States, such as Boston University, Albany Medical College, and Harvard Medical School. Additionally, there is tight collaboration and scholarly interchange among European and American nations, particularly in highly productive countries, such as the University of California System, Veterans Health Administration, and Mayo Clinic. In addition, there are some highly cooperative institutions located in China, but more show domestic cooperation, such as Capital Medical University, Beijing Normal University, Chinese University of Hong Kong, and Chinese Academy of Sciences.

In the past 10 years, a total of 25,944 authors have been devoted to the study of mild cognitive impairment. In this study, authors cited more than 500 times were defined as core researchers and a total of 105 authors were finally considered as core researchers. As shown in Table 3, only two of the top 10 prolific authors are from Asia, while the rest are from Europe and the United States. Figure 5A clearly shows the difference between the authors’ volume of postings. Combined with the documents and the impact index, Petersen, Ronald C, Shen, Dinggang, and Knopman, David S played a key role in this field. Figure 5B shows a superimposed annual view of the core researcher collaboration network. Collaborations between authors are mostly concentrated from 2015 to 2018, with red representing newer collaborations.

The top 10 authors with the most co-cited times are all from European and American countries, among which 5 are from the United States and 2 are from the same institution: Mayo Clinic. Petersen, Ronald C far exceeds other authors with a total of 6,267 co-citations, which shows his outstanding position in this field. According to their co-citation relationship, co-cited authors are divided into six categories (Figure 5C). Figure 5D shows the influence of co-cited authors in this field.

A total of 806 journals reported studies on mild cognitive impairment, and 15,979 journals were cited by these journals. As shown in Figure 6A, the Journal of Alzheimer’s Disease was the most productive journal (714, 37.58%), followed by Frontiers in Aging Neuroscience (313, 16.47%) and PLoS One (129, 6.79%). The top ten journals are listed in Table 4, most of them are from Europe and America, of which three belong to the United States and three belong to the United Kingdom. Four journals have an impact factor > 5, including Frontiers in Aging Neuroscience (5.702), Alzheimer’s & Dementia (16.655), International Psychogeriatrics (7.191), and Neurobiology of Aging (5.133).

The foundation of current research frontiers is earlier research that was published in co-cited publications. The co-citation analysis was conducted by the VOSviewer (Figure 6B). In the top ten co-cited journals, five are from the United States and three are from the United Kingdom, which shows the high academic influence of these two countries. Besides six have an impact factor > 5 and five belong to Q1, demonstrating the high quality of co-cited journals (Table 5).

The dual-map overlay of journals refers to the overlaying of citing and cited journals on a single graph to investigate the relationship between journals. The left side of the graph is the citing journal, the right side is the cited journal, and the color path represents the citation relationship in Figure 6C. The research of citing journals mainly refers to (1) molecular, biology, and immunology; (2) medicine, medical, and clinical; (3) neurology, sports, ophthalmology; (4) psychology, education, health, while most publications of cited journals come from (1) molecular, biology, genetics; (2) health, nursing, medicine; (3) psychology, education, health. This shows that genetics, fundamental medical fields, psychological fields, and clinical fields are all tightly related to MCI. The source dynamics are presented in Figure 7 displaying the cumulate and annual occurrences of the 10 journals with the largest number of publications in this field.

Co-cited reference refers to being cited by other publications at the same time. These documents are inextricably linked to form a co-cited literature network, which is an invaluable tool for analyzing high-quality research dynamics in this field (Effah et al., 2023). Co-citation reference analysis helps grasp the research trends and high-quality research progress in this field and related research fields. A total of 122,253 articles were included in the analysis, and the top 10 most-cited articles are listed in Table 6. The guideline “The diagnosis of mild cognitive impairment due to Alzheimer’s disease: recommendations from the National Institute on Aging-Alzheimer’s Association workgroups on diagnostic guidelines for Alzheimer’s disease” in the Alzheimer’s & Dementia (IF: 16.655) ranked first with 474 co-citations. Among the highly co-cited references, the most popular topics included the diagnosis, biomarkers, definition, and clinical guidelines of Alzheimer’s disease and mild cognitive impairment. Almost Half of the top ten co-cited documents were published in Alzheimer’s Dementia (IF: 16.655), which is the most prestigious top journal in this field. In addition, Lancet (IF: 202.731) and Lancet Neurology (IF: 59.935) are also very authoritative among peer-reviewed journals.

As the illustration in Figure 8A shows, different colors represent the corresponding year, and the connection represents the co-citation relationship. After cluster analysis, this literature was divided into 18 categories, such as Alzheimer’s disease (#1), diagnostic criteria (#3), biomarkers (#8), and functional nuclear magnetic resonance (#18). In order to better predict the future research direction and understand the current research topics of mild cognitive impairment, the cluster map of co-cited documents from 2022 to 2023 was superimposed on the original map (Figure 8B). The categories covered by the green line represent areas where the latest research is still being devoted, such as Herbal medicine (#0), physical activity (#7), cognitive training (#12), and amyloid-beta (#13).

Keyword analysis can reflect the evolution and hotspots of a research field, especially the frontiers of research. According to the high-frequency keywords of the co-occurrence network, the four keywords “Alzheimer’s disease,” “mild cognitive impairment,” “dementia,” and “diagnosis” ranked the top four with a total occurrence of 4,040 times, 3,497 times, 3,121 times and 736 times, respectively (Figure 9A), which revealed that mild cognitive impairment was closely related to dementia and Alzheimer’s disease, and highlighted the importance of early diagnosis of mild cognitive impairment. In addition, the high-frequency keywords of the co-occurrence network are divided into 4 categories through cluster analysis (Figure 9B). #1: Neuroimaging is an important diagnostic tool for mild cognitive impairment, which currently includes magnetic resonance imaging (MRI), PET, single-photon emission computed tomography (SPECT) imaging, and so on (Red cluster including “hippocampus,” “functional magnetic resonance,” “cortical thickness,” “structural MRI,” “white matter hyperintensities,” and “electroencephalography”); #2: Biomarkers have become an indispensable diagnostic criterion for mild cognitive impairment, and the two most widely studied markers are reflected Aβ deposition and tau deposition (Blue cluster including “amyloid-beta,” “biomarker,” “cerebrospinal fluid,” “clinical-diagnosis,” “plasma,” “progression,” and “tau”); #3: Cognitive tests are the important evidence for assessing the presence of objective cognitive decline, which plays a key role in the diagnosis of mild cognitive impairment (Yellow cluster including “accuracy,” “assessment moca,” “brief screening tool,” “cognitive screening,” “guidelines,” “mini-mental state examination,” and “neuropsychological tests”); #4: There are currently no approved pharmacologic for treating patients with MCI, but cognitive training and regular exercise has proved to be beneficial measures (Green cluster including “activities of daily living,” “aerobic exercise,” “caregivers,” “cognitive training,” “cognitive reserve,” “donepezil,” “efficacy,” and “intervention”).

Burst keyword refers to a sudden spike in the frequency of keywords over a short period. By examining the burst keywords, research hotspots and frontiers in this topic can be identified (You et al., 2021). The red nodes in Figure 10A represent bursts of keyword citations. These hot topics included neuroimaging (functional magnetic resonance imaging, # 0), cognitive test (moca, # 3), classification (vascular dementia, # 4), biomarkers (tau, # 5), and treatment (intervention, # 7) of MCI. In the top 25 keywords with the strongest citation bursts over the past decades, machine learning ranked first with the highest burst strength (18.25), followed by vascular dementia (17.47), voxel based morphometry (15.51), hippocampal atrophy (15.27), and tau (13.18) (Figure 10B). The research of tau begins from 2013 and burst from 2020 to 2023. As is shown in the figure, machine learning (18.25), tau (13.18), networks (13.18), EEG (10.44), type 2 diabetes mellitus (8.47), is the current research hotspot.

The number of annual publications in the first stage (2013–2018) showed a slow growth trend, the main reason may be that the concept of MCI is evolving. MCI started as a research term but gradually came into use in clinical practice. Due to the evolving concept of MCI and the lack of a unified consensus, there were no breakthroughs in the study of MCI at this stage (Petersen et al., 2014). Saunders et al. (2018) showed the direction of MCI research in 2018, and then the second phase grew rapidly. They thought that further research was needed in multi-domain biomarkers, more accurate neuroimaging techniques, more sensitive neuropsychological testing, and risk factors. Since then many studies have been conducted intensively based on these directions, and research on MCI has entered a phase of rapid development. The practice guidelines were updated in 2018 to guide and standardize clinical diagnosis and treatment of MCI and to facilitate advances in clinical practice (Petersen et al., 2018). A novel neuropsychological criterion has been proved that could improve the accuracy of MCI diagnosis in 2019, which further promoted the development of this field (Edmonds et al., 2019). Jia et al. (2020) proposed prevention strategies and integrated management in 2020 to reduce the prevalence of MCI and carry out early intervention, which was a beneficial exploration (Jia et al., 2020).

According to the collaborative network of countries/regions, institutions, and authors, the trend that the United States was far ahead, China was catching up, and Europe was an important center of scientific collaboration could be determined. The reason for the amazing dominance of the United States in the field of MCI is that many prominent authors as well as advanced research institutions are located in the US. The US is the maker of important concepts and diagnostic standards in the MCI field (Rabinovici et al., 2019). The deeper reason may be the highly developed economy of the United States to support research, the comprehensive education system to cultivate high-quality talents, and the favorable talent system to attract the gathering of talents. China’s high volume of publications and impact index may be attributed to its rapidly developing economy and the emphasis on MCI after entering an aging society. However, there is little international cooperation in China, which may be due to geographical constraints and a lack of creative research to break through academic barriers. A significant contribution to the development of the MCI field was made by the work of Petersen, and Ronald’s team on early biomarkers of MCI and risk factors for the progression of MCI to dementia. For example, Potential predictors like neuropsychiatric symptoms, olfactory deficits, and multiple metabolic pathways were identified (Geda et al., 2014; Roberts et al., 2016).

Alzheimer’s Dementia is regarded as one of the most significant journals based on the impact factor, the number of citations, and the H-index. The magazine, a leader in the field of cognitive science, is committed to publishing ground-breaking and exciting articles on a variety of subjects, including epidemiology, diagnostic criteria, and more (Bocchetta et al., 2015; Rajan et al., 2021; Festari et al., 2023).

Based on the literature co-citation and keyword analysis, the following promising novel studies in the field of MCI are proposed to guide valuable future research directions.