Incidence Rates of Dementia, Alzheimer Disease, and Vascular Dementia in the Japanese American Population in Seattle, WA

Amy R. Borenstein, Yougui Wu, James D. Bowen, Wayne C. McCormick, Jay Uomoto, Susan M. McCurry, Gerard D. Schellenberg, Eric B. Larson

There are few studies on the incidence of dementia in representative minority populations in the United States; however, no population-based study has been conducted on Japanese American women. We identified 3045 individuals aged 65+ with at least 1 parent of Japanese descent living in King County, WA in the period 1992 to 1994, of whom 1836 were dementia-free and were examined every 2 years (1994 to 2001) to identify incident cases of all dementias, Alzheimer disease (AD), vascular dementia (VaD), and other dementias. Cox regression was used to examine associations with age, sex, years of education, and apolipoprotein (APOE)-ε4. Among 173 incident cases of dementia, the overall rate was 14.4/1000/y, with rates being slightly higher among women (15.9/1000) than men (12.5/1000). Rates roughly doubled every 5 years for dementia and AD; the age trend for VaD and other dementias was less consistent. Sex was not significantly related to incidence of dementia or its subtypes in adjusted models. There was a trend for an inverse association with increasing years of education. APOE-ε4 was a strong risk factor for all dementias [hazard ratio (HR)=2.89; 95% confidence interval (CI), 1.88-4.46], AD (HR=3.27; 95% CI, 2.03-5.28), and VaD (HR=3.33; 95% CI, 1.34-8.27). This study is the first to report population-based incidence rates for both Japanese American men and women.