Incidence and prevalence of dementia in a multiethnic cohort of municipal retirees

BACKGROUND: Multiethnic population-based studies of dementia are lacking in the literature; therefore, we conducted a study to determine the incidence and prevalence of dementia among, black, white, and Hispanic municipal retirees age 50 and older. METHODS: In 1991, city of Houston municipal workers who retired between 1980 and 1984 received in-home screening for cognitive impairment using the Mini-Mental State Examination and were referred for comprehensive neurologic evaluation if indicated. Families of deceased retirees were interviewed, medical records were reviewed, and death certificates were obtained to determine case status of the retiree. Study participation was 90%. RESULTS: Crude prevalence of dementia, among retirees age 60 and older, was 2.65 per 100 population. Age-adjusted to the 1970 US population, age 60 to 80, the prevalence was 1.85 per 100 population. Age-adjusted prevalence of dementia was similar among Hispanic and black men, 4.75 and 4.80 respectively, and lowest among white men, 2.42 per 100 population. Forty-three percent of the prevalent cases (30% of the incidence cases) were not previously diagnosed. The cumulative incidence of dementia calculated to age 80 was 39% for Hispanic men, 28% for black men, and 14% for white men. Fifty-five percent of the incidence cases were diagnosed as having ischemic vascular dementia (IVD), 20% as having probable or possible Alzheimer's dementia (AD), and 25% as having unspecified dementia. CONCLUSIONS: Risk of dementia by age 80 was more pronounced for Hispanic and black men compared with white men. IVD was the predominant cause of dementia among both black and white men. Grouping Hispanics with whites may mask differences when studying dementia.