Familial aggregation of Alzheimer disease among whites, African Americans,and Caribbean Hispanics in northern Manhattan

Background: Alzheimer disease (AD) aggregates in families. Objective: To compare the familial aggregation and lifetime risk of AD to t he age of 90 years in the first-degree relatives of patients with AD and un related controls among Caribbean Hispanics, African Americans, and whites i n Washington Heights, Manhattan, New York, NY. Methods: Family history of AD and demographic information were obtained fro m informants of 435 patients with probable or possible AD concerning 1577 s iblings and parents and from 1094 controls without dementia concerning 3952 siblings and parents. Results: Lifetime risk of AD to the age of 90 years was 25.9% in relatives of patients and 19.1% in relatives of controls. Rate ratio (RR) for AD in r elatives of patients compared with relatives of controls was 1.5 overall (9 5% confidence interval [CI], 1.2-1.9), and was greater for siblings (RR, 1. 8; 95% CI, 1.2-2.5) than for parents (RR, 1.2; 95% CI, 0.9-1.8). Within eth nic groups, RR for AD among relatives was significantly elevated in whites (RR, 2.0; 95% CI, 1.2-3.3) and Hispanics (RR, 1.5; 95% CI, 1.1-2.1), but th e difference did not reach statistical significance in African Americans (R R, 1.4; 95% CI, 0.7-2.7). Risk of AD was greater among relatives who were w omen compared with men (RR, 1.5; 95% CI, 1.2-1.9). Conclusions: Familial aggregation of AD was increased among families of pat ients compared with those of controls in all 3 ethnic groups. Risk of AD wa s high est among siblings and women relatives.