Closing the Data Gaps on Trends in Dementia and Related Care in Low- and Middle-Income Countries

Population aging is a global phenomenon. A rapid rise in global dementia cases is a key consequence of population aging, with uneven trends in the current and projected prevalence around the world. Approximately 60% of all people living with dementia reside in low- and middle-income countries (LMICs) (1). By 2050, this figure is expected to rise to 71%, translating to nearly 100 million people (1). There is also evidence, mainly from high-income countries (HICs), that the impact of dementia on families and caregivers is substantial (2). There is an urgent need to develop strategies for dementia prevention, treatment, and care in LMIC settings that will bear the heaviest share of global dementia cases in the future. This supplement of JGMS largely represents research on trends in dementia and related care in HICs, yet there are articles with relevance for trends in LMICs as well.

In a comparative study of HIC trends in later-life memory function, Myrskylä et al. compared trends in scores on immediate and delayed word recall tests (3). They found that memory function in the 11 countries represented in the Survey of Health, Ageing and Retirement in Europe (SHARE) improved at a similar pace across countries over the period from 2004 to 2019. Interestingly, memory improvement over a similar time frame was modestly slower in England, and considerably slower in the United States, especially for those younger than age 75. The authors note that this pattern is consistent with prior research showing worse physical health and mortality outcomes in the United States compared to other HICs (4–6). In the case of memory function, the authors suggest that the slow pace of improvement in the United States may be due to the comparatively high prevalence of cardiometabolic dementia risk factors. Also, in this issue, Freedman et al. examined whether the recent downward trend in the population prevalence of dementia in the United States was affected by the coronavirus disease 2019 (COVID-19) pandemic (7). They found that declines in prevalence occurred both before (2011–2019) and through years extending into (2011–2021) the pandemic but were accelerated for the full period relative to the pre-pandemic years. Several additional findings are noteworthy. First, the authors found that although dementia incidence initially increased with the onset of the pandemic, it then declined at a rate more consistent with the ongoing pre-pandemic trend (7). Second, they found that mortality during the pandemic increased sharply among those with dementia, which was a key contributor to accelerating declines in prevalence (7). Finally, they showed that compositional changes in the population (eg, increasing educational attainment and decreasing age structure) appeared to play less of a role in declining dementia prevalence for the 2011–2021 period than they did for the period prior to the COVID-19 pandemic (7). Together, these 2 papers offer complementary insights into the changing landscape of cognitive health and dementia in HICs and the United States.

Whether similar trends of secular improvements in memory function and declining dementia incidence and prevalence can be expected in LMICs as economic development continues is an open question. Educational access and quality have largely been improving in several LMIC settings in recent decades, especially for women, despite continued inequities in education at national and subnational levels (8). Although the full extent of COVID-19-related disruptions to educational access and outcomes is yet to be fully understood with respect to future dementia trends (9), it is plausible to expect that dementia prevalence may decline as population educational attainment in LMICs improves (10). However, worsening cardiometabolic health trends in many LMICs (11), thought in part to be due to the proliferation of “Western” diets characterized by processed foods, sugar-sweetened beverages, red meat, and refined carbohydrates, may at least partially offset the benefits of education with respect to dementia trends. High-quality longitudinal data from LMIC settings are urgently needed to assess dementia trends in these settings and evaluate if and how they may diverge from those observed in HIC settings.

The 2 articles in this supplement that draw upon data from LMIC settings both focus on caregiving. Using harmonized data from the Gateway to Global Aging Data in China, India, and Mexico, Park et al. found a high prevalence of adults aged 65 and older in 2018 with both cognitive impairment and difficulty with at least one activity of daily living (ADL) or instrumental activity of daily living in each country: over one third in Mexico, nearly half in China, and over half of the population in India (12). These findings suggest a substantial need for caregiving in each country. The authors found that while unpaid caregiving from family or friends was common, not all older adults who needed care received it, especially those who lived alone (12). Recognizing that family caregiving networks may not be sufficient as populations continue to age, Jin et al. used data from the Chinese Longitudinal Healthy Longevity Surveys to project that the cost of long-term care for older adults with cognitive impairment and ADL disability in China is likely to increase more than eightfold from 197 billion Yuan in 2022 (~$27 billion USD) to 1 697 billion Yuan in 2040 (~$233 billion USD) (13). These studies show that resources and support for both unpaid and paid care for older adults with dementia in LMICs are needed. Evidence-based policies need to be implemented to ensure that such care is available and accessible for the growing segment of the population that will need it in the future.

A key challenge to the design of policies to support aging populations in LMICs is the substantial data gaps that remain with respect to trends in population dementia prevalence, incidence, distribution, and care-related outcomes over time. Although projections have been made with respect to the caregiving and financial costs associated with dementia, the quality of such projections is only as good as the data underlying them. Many LMICs with aging populations lack high-quality, population-based, and longitudinal data on cognitive impairment, dementia, disability, and the relevant covariates needed to understand trends in and risk factors for these outcomes. However, innovations in data infrastructure and harmonization are currently underway. The International Research Network of the Harmonized Cognitive Assessment Protocol (HCAP) coordinates and supports the harmonization of the content and methodology of cognitive aging and dementia studies around the world. The current pool of existing and planned HCAP studies represents approximately 75% of adults ages 65 and over around the world, and will be an increasingly valuable data resource for understanding global dementia trends, especially as HCAP studies in LMICs continue to collect data longitudinally (14). The Gateway to Global Aging Data is a valuable open-access resource for data users, which provides harmonized data sets and documentation on longitudinal studies of aging around the world, including HCAP studies. Continued investments in primary data collection studies in LMICs and infrastructure resources to promote the harmonization of such studies will help to promote research on dementia trends and ultimately support the development of evidence-based policies from a global perspective.

Funding

This work was supported by the National Institute on Aging of the National Institutes of Health (R01AG069128 and R01AG070953 to L.C.K.). This article appears as part of a supplemental issue on Multidisciplinary Perspectives on Dementia and Related Population Health Trends, which was supported by the Michigan Center on the Demography of Aging at the University of Michigan, with funding from the National Institute on Aging of the National Institutes of Health (P30AG012846).

Conflict of Interest

None.