Introduction to Supplement on Multidisciplinary Perspectives on Dementia and Related Population Health Trends.

Alzheimer’s disease and Alzheimer’s-disease-related dementias (hereafter, dementia) are a set of conditions involving impaired memory and other cognitive processes that interfere with daily functioning. Like other chronic conditions, the age-specific incidence of dementia rises sharply with age (1). Worldwide, significant increases in the number of older adults living with dementia are anticipated in the coming decades—from 55.2 million in 2019 to 78 million in 2030 and 139 million in 2050 (2)—unless effective interventions or treatments that forestall the onset of dementia are developed and widely adopted (3). The prevalence of dementia is expected to increase more rapidly in low- and middle-income countries (LMICs) than in high-income countries in the coming decades (4). This growth is likely to place significant pressures on families, who provide the bulk of care in many countries, and, particularly in high-income countries, on publicly financed services.

The papers in this supplemental issue are an outgrowth of the May 2023 annual meeting of the Michigan Center on the Demography of Aging’s (MiCDA) TRENDS network. TRENDS is a network of researchers working to accelerate scientific understanding of population-level changes over time in late-life disability, death, and health. The May 2023 meeting focused on updating our understanding of dementia and dementia care trends both in the United States and internationally. MiCDA and the TRENDS network are supported by a grant from the National Institute on Aging (P30AG012846).

This supplemental issue is also a follow-up to a 2018 supplemental issue of the Journals of Gerontology: Series B, undertaken by MiCDA’s TRENDS network. That issue featured 6 national studies and 3 subnational studies, each focused on a unique aspect of dementia trends. Six cross-cutting themes were identified in that issue (5): (1) dementia is becoming less prevalent in the United States overall, but not for all population groups; (2) some groups of older adults in the United States have experienced declines in the number of years lived with dementia; (3) racial and socioeconomic disparities in dementia are large and not diminishing over time; (4) rising levels of educational attainment partially account for dementia trends, and more research is needed to better understand the role of cardiovascular risk factors; (5) postponing the onset of dementia is the most effective way to reduce the size of the population living with dementia; and (6) close attention to dementia measurement challenges is critical.

The papers in this current supplemental issue grow our understanding of dementia and dementia care trends in 2 complementary ways: expanding our understanding of population trends in cognitive impairment and dementia from several high-income countries, and exploring trends and projections in care and related costs for older adults with dementia across high-income and middle-income countries (6–11). Two additional editorials in this issue focus on cross-cutting topics: approaches to handling practice effects in national studies of dementia trends, and current knowledge and data gaps in the study of dementia and related care trends in LMICs (12,13).