RACIAL/ETHNIC DIFFERENCES IN RATES OF DEMENTIA INCIDENCE AMONG THE OLDEST-OLD

Abstract

By 2060 there will be 9.5 million individuals age 90+ in the United States and over one third will be Non-White. In younger elderly, there are marked differences in rates of dementia by racial/ethnic groups, showing increased rates for Blacks and decreased rates for Asians. However, it is completely unknown if these discrepancies also occur in the oldest-old. We established a cohort of 2,351 members of Kaiser Permanente Northern California (KPNC) health-plan who, in 2010, were >age 90, with no diagnoses of dementia. Dementia diagnoses (ICD-9 codes 331.0, 290.0–290.4x, 294.1, 294.2x, and 294.8) made in primary care, neurology, memory clinics, and psychiatry were abstracted from electronic medical records from 1/1/2010–12/31/2015. We estimated dementia incidence rates standardized to the 2000 US Census 90+ year-old population by race/ethnicity. Cox proportional hazard models (age as time scale) evaluated the association between racial/ethnic groups and dementia risk. Participants were censored at dementia diagnosis, death, >90 day gap in health plan membership, or end of study. The mean age in 2010 was 93.1 (range: 90–109). The cohort is 65% female, 72% White (N=1,702), 16% Black (N=375), 4% Latino (N=105) and 7% Asian (N=169). 771 members (32.8%) were diagnosed with dementia during the 5-year follow-up period. The mean age of dementia diagnosis was 95.48 (SE=0.10) and was similar across racial and ethnic groups: 95.56 (SE=0.11) for Whites, 95.21 (SE=0.23) for Blacks, 95.71 (SE=0.66) for Latinos, 95.28 (SE=0.31) for Asians. The overall age-adjusted incidence rate (aIR) was 100.5 per 1,000 person-years. Asians had the lowest incidence rates (aIR=89.3), followed by Whites (aIR=97.0), Latinos (aIR=105.8), and, lastly, Blacks who had the highest rates (aIR=121.5). In cox proportional hazard models adjusted for age as the time scale, education, sex, midlife and late-life vascular comorbidities, Blacks had significantly higher risk (aHR=1.28; 95%CI: 1.05–1.51), compared to Whites. These are the first estimates of dementia incidence in a diverse cohort of 90+ individuals. Patterns of racial/ethnic disparities in dementia seen in younger elderly continue after age 90. These estimates provide an important foundation for understanding the burden of racial disparities in dementia in the oldest-old, the fastest growing segment of the population.