P3‐541: FEMALE REPRODUCTIVE FACTORS AND THE RISK OF DEMENTIA: A NATIONWIDE COHORT STUDY

To investigate whether female reproductive factors are associated with dementia incidence. We identified 4,696,633 postmenopausal women without the history of any dementia using Korean National Health Insurance System Cohort. Data on reproductive factors was collected by self-administered questionnaire. The incidence of dementia was identified dementia diagnosis codes with prescription of an anti-dementia drug. Cox proportional hazards regression models were used to assess hazard ratios for dementia incidence according to reproductive factors. During the median follow-up of 5.74 years, there were 212,227 new cases of all-cause dementia (4.5%), 162,901 cases of Alzheimer's disease (3.5%), and 24,029 cases of vascular dementia (0.5%). In multivariate adjusted model, the hazard ratios (HR) and 95% confidence intervals (CI) of all-cause dementia were 1.15 (1.03-1.16) for the age at menarche ≥ 17 years compared with the age 13–14 years, 0.79 (0.77-0.81) for the age at menopause ≥ 55 years compared with the age < 40 years, and 0.81 (0.79-0.82) for fertility duration ≥ 40 years compared with fertility duration < 30 years. While having 1 parity (HR 0.89, 95% CI 0.85-0.94) and breast feeding < 6 months (HR 0.92, 95% CI 0.88-0.95) was associated with lower risk of dementia, having ≥ 2 parity (HR 1.04, 95% CI 0.99-1.05) and breast feeding ≥ 12 months (HR 1.14, 95% CI 1.01-1.07) were associated with higher risk of dementia than women with nulliparity or no breast feeding history. Use of HRT or OC was independently decreased the risk of dementia by 15% and 10%, respectively. Consistent results were noted for Alzheimer's disease and vascular dementia.