Dementia Prevalence, Incidence, and Mortality Trends Among U.S. Adults Ages 72 and Older, 2011-2021.

Background: U.S.-focused studies have reported decreasing dementia prevalence in recent decades, but have not yet focused on the implications of the coronavirus disease 2019 (COVID-19) pandemic for trends.

Methods: We use the 2011-2021 National Health and Aging Trends Study (N = 48 065) to examine dementia prevalence, incidence, and mortality trends among adults ages 72 and older, and the contribution to prevalence trends of changes in the distribution of characteristics of the older population ("compositional shifts") during the full and prepandemic periods. To minimize classification error, individuals must meet dementia criteria for 2 consecutive rounds.

Results: The prevalence of probable dementia declined from 11.9% in 2011 to 9.2% in 2019 and 8.2% in 2021 (3.1% average annual decline). Pre-pandemic declines continued for women and non-Hispanic White individuals and emerged over the 2011-2021 period for men and those ages 80-89. Declines in dementia incidence were stronger for the 2011-2021 period than for the prepandemic period, while mortality among those with dementia rose sharply with the onset of the COVID-19 pandemic. Shifts in the composition of the older population accounted for a smaller fraction of the decline over the full period (27%) than over the prepandemic period (45%).

Conclusions: Declines in dementia prevalence continued into years marked by onset of the COVID-19 pandemic, along with declines in incidence and sharp increases in mortality among those with dementia. However, declines are no longer largely attributable to compositional changes in the older population. Continued tracking of dementia prevalence, incidence, and mortality among those with and without dementia is needed to understand long-run consequences of the pandemic.