Life long endogenous estrogen exposure and later adulthood cognitive function in a population of naturally postmenopausal women from Southern China: The Guangzhou Biobank Cohort Study

Background: Estrogen has neurotrophic and neuroprotective properties in animal and in vitro studies. Epidemiological studies are inconclusive, but suggest a positive association between endogenous estrogen exposure (measured by reproductive period, the number of years between menarche and menopause) and later life cognitive function. Methods: Structural equation modeling was used in a cross-sectional study of 11,094 naturally postmenopausal multiparous Chinese older (≥50 years) women from the Guangzhou Biobank Cohort Study (phases 2 and 3) to assess the interrelationship of four proxies of higher endogenous estrogen exposure (longer reproductive period, older age of first pregnancy, lower parity and shorter average duration of breast feeding per child) with immediate and the delayed 10-word recall score in phases 2 and 3, and with the mini-mental state examination (MMSE) score in phase 3 (5641 women). Results: Adjusted for age, education, childhood and adulthood socio-economic position and physical activity, longer reproductive period was associated with higher scores (0.02 words per year, 95% confidence interval (CI) 0.008-0.02 for delayed recall and 0.05 MMSE score, 95%CI 0.04-0.07, respectively). Lower parity and shorter average duration of breast-feeding per child were also associated with better cognitive function. Conclusions: In a large cohort of naturally postmenopausal Chinese women proxies of greater endogenous estrogen exposure were associated with better cognitive function. These findings support biological evidence for a cognitively protective role of endogenous estrogen.