Public Health.

Background: Illiteracy is highly prevalent in older women than in men, but whether the impact of illiteracy on dementia risk is differed by gender remains unclear.

Method: We enrolled 5,217 non-demented older adults aged ≥ 60 years from the Korean Longitudinal Study on Cognitive Aging and Dementia. Presence of illiteracy was assessed by research nurses and the diagnoses of incident dementia and Alzheimer's disease (AD) were made by standardized diagnostic interview by geriatric psychiatrists. Neuropsychologists assessed the cognitive performance by using Korean version of Consortium to Establish a Registry for Alzheimer's Disease Assessment Packet Neuropsychological Assessment Battery. Multivariate Cox proportional hazard regression and linear mixed model analyses were used to identify the impact of illiteracy on the risks of all-cause dementia/AD and cognitive decline during the 8-year follow-up respectively.

Result: Totally, 283 (98 men [4.4%]; 185 women [6.2%]) cases of all-cause dementia and 227 (71 men [3.2%]; 156 women [5.2%]) cases of AD were identified during the follow-up period (5.8 ± 2.4 years). Among 901 illiterate participants, 9 (7.9%) men and 101 (12.8%) women developed all-cause dementia whereas 5 (4.4%) men and 89 (11.3%) women developed AD. Illiteracy was found to pose 2.8-fold (Hazard Ratio [HR] = 2.79, 95% Confidence Interval [CI] = 1.95 - 3.99) and 2.9-fold (HR = 2.89, 95% CI = 1.97 - 4.25) increased risks of all-cause dementia and AD respectively in women. The HRs for association of illiteracy with all-cause dementia (HR = 2.48, 95% CI = 1.66 - 3.68) and AD (HR = 2.54, 95% CI = 1.66 - 3.90) risks remained significant even when we separately analyzed the less educated women (educational years ≤ 6 years, n = 1,830). However, there was no significant association in men. The impact of illiteracy on the progression of cognitive decline was more pronounced in women (β = -0.962, SE = 0.147) than in men (β = -0.618, SE = 0.338).

Conclusion: The impact of illiteracy on dementia risk may be more significant in women than in men, irrespective of the educational attainment of the study population. Illiterate older women should be considered the primary target population for dementia prevention strategies.