Short-Term Changes in the Prevalence of Probable Dementia: An Analysis of the 2011-2015 National Health and Aging Trends Study.

Objectives: Studies have reported decreasing dementia prevalence in recent decades in the United States. We explore with a new national data source whether declines have occurred since 2011, whether trends are attributable to shifts in dementia incidence or mortality, and whether trends are related to shifts in population composition or subgroup prevalence.

Methods: We use the 2011-2015 National Health and Aging Trends Study (N = 27,547) to examine prevalence of probable dementia among the 70 and older population. To minimize the influence of potential learning effects on prevalence rates, we require individuals to meet probable dementia criteria at two consecutive rounds.

Results: Prevalence of probable dementia declines over this period by 1.4% to 2.6% per year. Declines are concentrated among women, non-Hispanic white and black groups, and those with no vascular conditions or risk factors. The latter group also has experienced declines in dementia incidence. Declines in prevalence are largely attributable to age- and education-related shifts in population composition.

Discussion: Given the role of age and educational composition in short-term declines, the United States is likely to continue to experience short-term declines in dementia prevalence. However, persistently high rates among minority groups, especially of Hispanic origin, are concerning, and, barring new treatments, long-run trends may reverse course.