Abstract MP19: Patterns of Early-Onset and Late-Onset Dementia Incidence in the Dementia Risk Pooling Project

Introduction: Early-onset dementia (EOD) is defined as dementia diagnosed before age 65. While much is known about late-onset dementia (LOD), research on EOD is scarce. The Dementia Risk Pooling Project (DRPP) harmonized data from nine community-based prospective studies, including under-represented racial/ethnic groups. We hypothesized that EOD incidence rates are higher for men than women, and non-Hispanic (NH) Black participants than other race/ethnicity groups. Methods: We used data from eight DRPP cohorts: Age, Gene/Environment Susceptibility-Reykjavik Study, Whitehall II study, Atherosclerosis Risk in Communities Study, Cardiovascular Health Study, Honolulu-Asia Aging Study, Multi-Ethnic Study of Atherosclerosis, Sacramento Area Latino Study on Aging, and six Framingham Heart Study cohorts. Individual data were pooled and rigorously harmonized. Race/ethnicity was categorized as self-reported Hispanic, NH White, NH Black, and NH other/unknown. Crude incidence rates and ratios were calculated per 10,000 person-years with 95% confidence intervals. Results: The analytic sample consisted of 56,607 participants, who experienced 7,504 cases of LOD and 124 cases of EOD over a median follow-up of 19.13 (IQR 10.46 - 31.11) years. EOD and LOD incidence rates per 10,000 person-years were 1.95 (95% CI 1.62 - 2.32) and 123.35 (95% CI 120.49 - 126.26), respectively. Compared to women, men had 1.17 (95% CI 0.82 - 1.66) times the rate of EOD but 0.82 (95% CI 0.79 - 0.86) times the rate of LOD. Similarly, compared to NH Whites, Hispanics and participants of other or unknown race/ethnicity had higher rates of EOD but lower rates of LOD. NH Blacks had a higher rate of both EOD and LOD compared to NH Whites, but the association with EOD was more pronounced. Conclusion: In this multi-cohort study with individual participant data, EOD and LOD incidence rates were different across sex and race/ethnicity groups. Some of these differences may be due to longer life expectancy in women and some race/ethnicity groups.