Relationship of age, education, and occupation with dementia among a community-based sample of African Americans

C. M. Callahan, K. S. Hall, S. L. Hui, B. S. Musick, F. W. Unverzagt and H. C. Hendrie
Department of Medicine, Indiana University School of Medicine, Indianapolis, USA.

OBJECTIVE: To explore the relationship between age, education, and occupation with dementia among African Americans. DESIGN: Community-based survey to identify subjects with and without evidence of cognitive impairment and subsequent diagnostic evaluation of a stratified sample of these subjects using formal diagnostic criteria for dementia. SETTING: Urban neighborhoods in Indianapolis, Ind. SUBJECTS: A random sample of 2212 African Americans aged 65 years and older residing in 29 contiguous census tracts. MEASUREMENTS: Subjects's scores on the Community Screening Instrument for Dementia (CSI-D), formal diagnostic clinical assessments for dementia, years of education, rural residence, primary occupation, self-reported disease, and alcohol and smoking history. Caseness was defined by four separate criteria: (1) cognitive impairment as defined by the subject's performance on the CSI-D cognitive scale; (2) cognitive impairment as defined by the total CSI-D score that included a relative's assessment of the subject's functional abilities; (3) dementia as defined by explicit diagnostic criteria; and (4) possible or probable Alzheimer's disease as defined by explicit diagnostic criteria. RESULTS: The mean age was 74 years (age range, 65 to 100 years), 65% of subjects were women, the mean education was 9.6 years (age range, 0 to 16 years), 98% of the subjects were literate, and 32% reported living in a rural area until age 19 years. Service, domestic, and production occupations accounted for 55.2% of the subjects' primary occupations with a mean of 25.8 years (range, 1 to 75 years) in the primary occupation. Years of education, rural residence to age 60 years, and primary occupation were highly correlated. Caseness defined by any of the four criteria was associated with functional impairment, but the frequency of impairment increased with increasing diagnostic specificity. Age, education, and rural residence to age 60 years were significantly independently associated with caseness for cognitive impairment, dementia, and Alzheimer's type dementia. White-collar occupation was independently associated only with caseness for cognitive impairment. History of stroke was associated with caseness for cognitive impairment and dementia but not Alzheimer's disease, while history of smoking was negatively correlated with Alzheimer's disease. CONCLUSIONS: Education was independently associated with cognitive impairment and dementia among a representative community-based sample of African Americans and the association remains significant across a variety of sensitivity analyses designed to control for measurement and confounding biases. The potential protective role of education against the development of dementia among African Americans deserves further evaluation.