Illiteracy and the incidence of Alzheimer's disease in the Yonchon County survey, Korea

Background: This study aims to establish the incidence rates of Alzheimer's disease (AD) and to understand the relations between illiteracy and AD in the Korean Yonchon survey cohort. Methods: A community-based, dementia-free cohort of 966 people aged 65 years and older was followed up for an average of 5.4 ± 1.60 years to detect incident AD cases using a two-phase procedure. Age-specific incidence rates were calculated using a person-years approach with Poisson distribution confidence intervals. Data were analyzed using the Cox proportional hazards model to find the hazard ratio of illiteracy. Results: The participating percentage of the survivors was 86.4% and 74 subjects were diagnosed with AD. Incidence rates per 1000 person-years were 20.99 (95% CI 16.48 to 26.35) for AD. The hazard ratio of illiteracy was 1.78 (95% CI 1.08 to 2.93) adjusted for age, sex, educational level. AD developed more rapidly with aging in the illiterate group than in the literate group. Conclusions: Illiteracy is associated with a higher risk of AD and the risk increases with age.