Longitudinal studies examining the effect of endogenous estrogens on dementia risk are needed to understand why women have higher dementia incidence than men after age 85.
A population-based sample of women with natural menopause (N = 1364) from Gothenburg, Sweden, was followed from 1968-2012. Information on endogenous estrogens (age at menarche and menopause, number of pregnancies, and months of breastfeeding) was obtained from interviews in 1968-1992. Dementia was diagnosed according to established criteria based on information from neuropsychiatric examinations and close informant interviews.
We found that longer reproductive period was associated with increased risk of dementia (hazard ratio [HR] per year 1.06, 95% confidence interval [CI] 1.03-1.20) and Alzheimer’s disease (AD) (1.06, 1.02-1.11), particularly for those with dementia (1.10, 1.04-1.17) and AD (1.15, 1.06-1.26) onset after age 85.
These results may explain why women have higher dementia incidence compared to men after age 85, the age with the highest number of dementia cases.

© 2020 The Authors. Alzheimer’s & Dementia published by Wiley Periodicals LLC on behalf of Alzheimer’s Association.