The Effects of Estrogen on the Risk of Developing Dementia: A Cohort Study Using the UK Biobank Data

OBJECTIVES : The protective role of estrogen in the development of dementia remains uncertain. We investigated the role of lifetime cumulative exposure to estrogen in dementia in the UK Biobank. METHODS : Reproductive characteristics, including estrogen length and history of surgery (hysterectomy/oophorectomy), were used as exposure variables. Cox Proportional Hazard models were used to estimate hazard ratios (HR) for the development of dementia. RESULTS : 273,260 female participants were included in this study. Compared to women with the shortest estrogen length, women with the longer estrogen length (38−42) had a 28% decreased risk of dementia (HR= 0.718, 95% confidence interval (CI) =0.651-0.793). Women with later last age at estrogen exposure (50−52) had a 24% decreased risk for dementia (HR=0.763, 95% CI =0.695-0.839) compared to women with younger age at last estrogen exposure (≤45). Later age at menarche (≥15) was associated with a 12% increased risk for dementia (HR=1.121, 95% CI =1.018-1.234) compared to women with earlier age at menarche (≤12). Women with a history of surgery had an 8% increased risk of dementia (HR=1.079, 95% CI=1.002-1.164) compared to women without a history of surgery. CONCLUSION : This study found that more prolonged exposure to estrogen (longer estrogen length and later age at last estrogen exposure) had a decreased risk for dementia, and shorter exposure to estrogen (later age at menarche and history of reproductive surgery) had an increased risk for dementia. Based on the results of this study, estrogen might have a protective role in women in the development of dementia.