In late 2019, the novel coronavirus SARS-CoV-2 was identified as the cause of COVID-19, a respiratory disease with varying individual severity. In March 2020, as the disease was spreading worldwide, the World Health Organization (WHO) declared COVID-19 a pandemic. Research and experience have shown that COVID-19 severity and case-fatality are associated with the individual's age and immune status (1). Older age is thus considered a risk factor. The mortality rate is higher in the elderly due to several characteristics such as comorbidities, lower antibody levels, and polypharmacy, among others (2). Various governmental guidelines on COVID-19 have thus focused on older adults (3).

Social isolation is a useful measure for controlling the spread of infectious diseases or protecting high-risk groups from negative health outcomes. However, social isolation can also result in sedentary behavior, which is detrimental to the prevention of physical, psychological, and social health problems (4). In older adults, social isolation can increase the risk of depression, anxiety, and suicide, with considerable impact on quality of life, burden of care, and use of resources. For example, Rana (5) described five reported cases of older adults who committed suicide due to recurrent depressive disorder. Older adults already suffering from mental disorders have been more vulnerable to COVID-19 and its social consequences (5).

Social isolation is difficult for people with dementia and their caregivers in this context. According to Dourado et al. (6), COVID-19 raised significant concerns in the management of care for people with dementia. This age group has experienced limited access to services and activities, resulting in aggravation of cognitive deficits, affecting such domains such as memory and orientation, besides behavioral impairments. Social isolation can also exacerbate preexisting stress, overburden, and depression in caregivers (6).

The pandemic has further aggravated the vulnerability of older adults, especially those with neurocognitive disorders such as Alzheimer's disease. For example, dementia can increase the risk of contracting COVID-19, due to difficulties in understanding or remembering the need for social isolation (6). The COVID-19 pandemic also involves caring for people with dementia and support from community centers for this patient population, when such centers are experiencing difficulties continuing their work (6). The main objective of this systematic review was thus to better understand the impacts of the COVID-19 pandemic on people with dementia and on their caregivers' mental health.

This systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) (7). The literature search was carried out from August 5 to 26, 2021, using the following electronic databases: Medline (PubMed) and Science Citation Index (Institute for Scientific Information – ISI). Based on Medical Subject Headings (Mesh), the search keywords included “COVID-19,” “pandemic,” “mental health,” “dementia,” “caregivers,” and “elderly” in the following combinations: “COVID-19 and mental health and elderly,” “COVID-19 and mental health and dementia,” “COVID-19 and dementia and caregivers,” “pandemic and mental health and elderly,” and “pandemic and anxiety.”

The search was performed according to the following PICOS:

Inclusion criteria were: (1) publications from 2020 to 2021, (2) only studies with older adults with cognitive impairment and/or their caregivers, (3) research on people with dementia (cognition, neuropsychiatric symptoms, and functionality) and their caregivers' mental health (burden, anxiety, and depression) during the COVID-19 pandemic, and (4) publications in the English language. The exclusion criteria were: (1) studies published prior to 2020 and (2) mental health studies during the COVID-19 pandemic without people with dementia and/or their caregivers.

Initially, 4,328 records were identified through the database searches: 3,304 in PubMed/Medline and 1,024 in ISI. The 149 studies that remained after application of the exclusion criteria were retrieved for potential use, and the information of the full-text version of each study was evaluated. The reference lists of all selected articles were cross-referenced. After duplicates were removed, the total number of studies decreased to 22. Figure 1 provides a flowchart of the different study selection phases. The included studies are shown in Table 1.

This systematic review aimed to elucidate the impact of the COVID-19 pandemic on people with dementia and on their caregivers' mental health. The database search yielded several articles related to the COVID-19 pandemic and dementia, but most of these studies addressed the mental health of health professionals, who are active on the front lines of the fight against the novel coronavirus. We also found studies on the mental health of older adults without neurocognitive disorders. Interestingly, there were few studies of people with dementia, possibly due to current limitations on research in this group. For example, standard neuropsychological assessment methods rely on face-to-face interactions, which were not possible due to social isolation. Social isolation requires modifications to study protocols for remote data collection to continue participants' assessments (6). We thus observed that many rating scales for measuring cognitive, behavioral, or mood symptoms in people with dementia were applied through videoconferencing or phone calls.

In most of the selected studies, caregivers helped people with dementia respond to the scales, a critical aspect of the assessments' reliability. Considering this study bias, Crivelli et al. (31) developed recommendations to support standardized clinical procedures that recommend data generation through teleneuropsychological assessments. For example, people with visual or auditory deficits, acute confusional states, or severe communication difficulties should not be evaluated using teleassessments, nor should they provide recorded verbal consent or an electronic signature. If tests are interrupted, they should be readministered from the beginning when contact with the patient is resumed, or it should be clarified that some qualitative data usually collected from face-to-face consultations are no longer acquired, which may limit recommendations and conclusions (31).

Concerning the studies' designs, we found only one longitudinal study. The cross-sectional studies used different methods of evaluation to assess the pandemic's impact. For example, Tsapanou et al. (16) provided a self-report questionnaire to caregivers of people with mild cognitive impairment or dementia related to changes in physical, psychological, and routine activities during the pandemic. Bouteleau-Bretonnière et al. (17) contacted caregivers of people with AD who were confined to their homes for nearly 2 months and asked about the changes in neuropsychiatric symptoms during this period. Mori et al. (24) compared the presence of depression in persons with Parkinson's disease and controls. Manini et al. (20) contacted caregivers of 109 community-dwelling adults with dementia who had a telephone follow-up after their hospital visits were canceled.

Interestingly, we found few studies evaluating cognition and level of functional impairment in people with dementia (9–11, 13, 17). Considering the different cognitive functions such as memory, attention, or executive function and their impact on different types of activities of daily living (basic and instrumental), it was not possible for the selected studies to examine which functions were most affected by social isolation. Therefore, further longitudinal studies should help to better understand the lockdown's impact on specific cognitive functions and routine activities to help develop interventions to attenuate the impact of social isolation on this population.

Social isolation is a measure to prevent spread of the novel coronavirus, but people with dementia and their caregivers have experienced changes in routine life, health services, and support activities as a result. Neuropsychiatric symptoms are a common feature in dementia, affecting 80% of patients over the course of the disease (6). Thus, most of the selected studies focused on changes in neuropsychiatric symptoms during social isolation. Overall, social isolation exacerbated or led to the manifestation of various neuropsychiatric symptoms. Agitation, delirium, irritability, apathy, aggression, anxiety, indifference, and altered mood were the most common symptoms found (9, 11, 14, 16, 18, 20, 21). Cohen et al. (18) found that new onset of behavioral symptoms or exacerbation of preexisting behavioral symptoms was positively correlated with patient's age and presence of anxiety reported before the epidemic and negatively correlated with global CDR score and the domains of memory, community affairs, and home and hobbies. Importantly, meaningful recreational activity has been shown to increase positive emotions, improve activities of daily living, and attenuate challenging neuropsychiatric symptoms (32). These findings may help develop potential digital delivery of non-pharmacological intervention programs, but further studies should explore differences in neuropsychiatric symptoms according to the type of dementia or patient's age at onset.

The COVID-19 pandemic has worsened the situation of families caring for people with dementia by delaying diagnosis and increasing the burden on caregivers (33). Caregivers have faced many challenges in caring for their loved ones, such as fear and concern about protecting them from SARS-CoV-2 infection, since recipients of care may not know how to follow the protective measures. Caregivers have had to reconcile the new challenges of care for their elders that already led to the burden of care (30). Furthermore, it is important to consider regional and cultural differences in caregiver support. For example, in Greece, Tsapanou et al. (16) reported that most families have lacked significant support during this period. In India, caregivers suggested several methods such as use of video-consultations, telephone-based support, and clinic-based in-person visits to meet their needs. They also requested more post-pandemic services (30). In Italy, caregivers with high resilience showed a more significant increase in anxiety levels during lockdown than caregivers with low resilience (27). There is thus a need to consider the development of specific interventions tailored to different cultural backgrounds and different types of dementia, such as early-onset dementia and more complex syndromes such as frontotemporal dementia (33).

Telemedicine has been a widely used method in this period. Lai et al. (29) studied whether telehealth would benefit people with dementia and their caregivers. The complementary telehealth delivered through video-conferencing apps was associated with more positive effects for community-dwelling older adults with neurocognitive impairment and their caregivers compared to conventional telehealth conducted by phone conversation only (29). In addition, there was a positive impact of telehealth via videoconferencing on cognition and a notable improvement in quality of life (29). One study (30) has suggested that online psychoeducational support and specific guidelines for care can meet caregivers' needs and contribute to their well-being. The use of technology by people with dementia and their caregivers depends on expectations, perceived skills, and expertise in using the devices (34). Some studies (12, 15) reported that many people with dementia were less likely to be digitally literate, making equal access to the services difficult. Therefore, technological initiatives should consider both people with cognitive impairment as well as different technology literacy levels.

Another question is whether COVID-19 has a different clinical presentation in older people. Compared to younger people, the effect of COVID-19 on geriatric patients may be more serious because of higher rates of chronic illness, resulting in more severe cases of the disease. Unlike younger people, who present such symptoms as fever, cough, and chest discomfort, older adults may manifest COVID-19 through atypical symptoms such as mental confusion, falls, decreased mobility, tachycardia, blood pressure changes, decreased appetite, difficulty swallowing, and urinary incontinence (35). Therefore, caregivers of older adults may have difficulty recognizing the disease, especially in people with dementia, in whom these symptoms are already common. Older adults with dementia may also have other comorbidities that mask the infection. Prevention is still the safest measure against COVID-19, but screening services should consider that in older people, the infection can manifest itself through atypical symptoms. Thus, every geriatric patient should be tested and observed for all presenting symptoms (35). Medical teams and caregivers must be aware of any changes older adults may present, and hospitals must be prepared for the possible diagnosis. Misdiagnosis can lead to severe complications from the infection (36).

This systematic review has some limitations that should be considered. The first is the topic's broad scope, encompassing studies with multiple methods and outcomes. The second difficulty is transposing current evidence from one continent to another or from specific sociocultural and economic realities to others. The selected studies are also methodologically heterogeneous, thus limiting the comparison of their findings.

There are few publications on the mental health of older persons with dementia and their caregivers during the COVID-19 pandemic compared to studies in other population groups. The selected studies were nearly unanimous in emphasizing that social isolation and withdrawal can lead to (or exacerbate) neuropsychiatric symptoms, motor difficulties, and cognitive decline. Caregivers have also suffered from the pandemic's impact, with an increase in the burden of care and symptoms of stress, depression, and anxiety. Both patients and caregivers have experienced radical changes in their routines that have affected their health and quality of life.

Few studies suggested measures to alleviate the difficulties of people with dementia and their caregivers. There are reports of the benefits of technology for communication and treatment via teleconsultations, but such technologies are still not widely known and not everyone has access to them, thus limiting their use by the target population. New forms of care and intervention are needed for older adults with cognitive impairment and their caregivers to prevent the intensification of their physical and psychological suffering.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

JG performed the systematic search and wrote the first draft. IL assisted with articles inclusion and exclusion. MD designed the systematic review, assisted with articles inclusion and exclusion and approved the final version. All authors contributed to the article and approved the submitted version.

MD receives research grants from the Brazilian National Council for Scientific and Technological Development (CNPq) and the Rio de Janeiro State Research Support Foundation (FAPERJ).

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.

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