The role of nativity in heterogeneous dementia incidence in a large cohort of three Asian American groups and white older adults in California

Introduction Literature shows lower dementia incidence in Asian American groups versus whites, varying by Asian ethnicity. One hypothesized driver is nativity differences (eg, healthy immigrant effect). Methods We followed a cohort of 6243 Chinese, 4879 Filipino, 3256 Japanese, and 141,158 white Kaiser Permanente Northern California members for incident dementia (2002 to 2020), estimating age-adjusted dementia incidence rates by ethnicity and nativity, and hazard ratios (HR) for nativity on dementia incidence using ethnicity-stratified age- and sex-adjusted Cox proportional hazards models. Results Dementia incidence appeared higher in foreign- versus US-born Filipinos (HR, 95% confidence interval: 1.39, 1.02 to 1.89); differences were small in Japanese (1.07, 0.88 to 1.30) and Chinese (1.07, 0.92 to 1.24). No nativity differences were observed among whites (1.00, 0.95 to 1.04). Discussion Nativity does not explain lower dementia incidence in Asian Americans versus whites, but may contribute to heterogeneity across Asian ethnicities. Future research should explore differential impacts of social and cardiometabolic factors.