The Association of Early Life Factors and Declining Incidence Rates of Dementia in an Elderly Population of African Americans.

Objectives: To explore the possible association of childhood residence, education levels, and occupation with declining incidence rates of dementia in 2 cohorts of elderly African Americans.
Methods: African Americans residing in Indianapolis without dementia were enrolled in 1992 and 2001 and evaluated every 2-3 years. The cohorts consist of 1,440 participants in 1992 and 1,835 participants in 2001 aged 70 years and older. Cox proportional hazard regression models were used to compare cohort differences in dementia and Alzheimer's disease (AD) risk.
Results: The 2001 cohort had significantly decreased risk of both incident dementia and AD (hazard ratio [HR]: 0.62/0.57 for dementia/AD). Years of education was associated with decreased risk of dementia (HR = 0.93; p = .0011). A significant interaction (p = .0477) between education and childhood rural residence was found for the risk of AD that higher education level is significantly associated with reduced AD risk (HR = 0.87) in participants with childhood rural residence, but no association in those with urban upbringing. The cohort difference for dementia rates were attenuated by adjusting for the 3 risk factors but remained significant (HR = 0.75; p = .04).
Discussion: These results emphasize the importance of early life factors including rural residence and education for the risk for dementia later in life.