Objective: Several cross-sectional studies have found an association between Alzheimer's disease (AD) and limited educational experience. It has been difficult to establish whether educational experience is a risk factor for AD because educational attainment can influence performance on diagnostic tests. This study was designed to determine whether limited educational level and occupational attainment are risk factors for incident dementia.

Design: Cohort incidence study.

Setting: General community.

Participants: A total of 593 nondemented individuals aged 60 years or older who were listed in a registry of individuals at risk for dementia in North Manhattan, NY, were identified and followed up.

Interventions: We reexamined subjects 1 to 4 years later with the identical standardized neurological and neuropsychological measures.

Main outcome measures: Incident dementia.

Results: We used Cox proportional hazards models, adjusting for age and gender, to estimate the relative risk (RR) of incident dementia associated with low educational and occupational attainment. Of the 593 subjects, 106 became demented; all but five of these met research criteria for AD. The risk of dementia was increased in subjects with either low education (RR, 2.02; 95% confidence interval [Cl], 1.33 to 3.06) or low lifetime occupational attainment (RR, 2.25; 95% Cl, 1.32 to 3.84). Risk was greatest for subjects with both low education and low life-time occupational attainment (RR, 2.87; 95% Cl, 1.32 to 3.84).

Conclusions: The data suggest that increased educational and occupational attainment may reduce the risk of incident AD, either by decreasing ease of clinical detection of AD or by imparting a reserve that delays the onset of clinical manifestations.