The effect of education on the incidence of dementia and Alzheimer's disease in the Framingham Study

OBJECTIVE: To evaluate whether low educational attainment is a risk factor for the incidence of dementia and Alzheimer's disease (AD) in the Framingham Study and to determine whether age at onset of dementia is earlier in persons with low educational levels. DESIGN: A community-based cohort was studied longitudinally for the development of dementia. Diagnosis was made according to strict criteria by two neurologists and a neuropsychologist. Subtype of dementia and year at onset were determined. Incidence rates were compared in three education groups: or = high school. PARTICIPANTS: A total of 3,330 men and women aged 55 to 88 years. RESULTS: During 17 years of follow-up, 258 incident cases of dementia, including 149 AD cases, were identified. Unadjusted incidence rates were significantly elevated (p < 0.05) for dementia and non-AD dementia among the least educated. The age-adjusted relative risk for subjects with a grade school education or less compared with those who earned a high school diploma was 1.31 (95% confidence interval CI, 0.90 to 1.90) for dementia generally, 1.04 (95% CI, 0.62 to 1.74) for AD, and 1.75 (95% CI, 1.03 to 2.98) for non-AD dementia. Age at onset of dementia did not vary by educational attainment. CONCLUSIONS: After age adjustment, low educational attainment was not a significant risk factor for the incidence of dementia generally or of AD. Low educational attainment was associated with increased risk of non-AD dementia, perhaps because of deleterious smoking habits and other risk factors for stroke in the least-educated individuals. Adequately adjusting for age and examining subtypes of dementia are important in assessing the influence of education on dementia incidence.