Objective: To investigate whether levels of endogenous hormones, in particular circulating oestrogens and SHBG, are associated with cognition in healthy postmenopausal women.
Design: Cross-sectional study.
Patients: Four hundred and two healthy postmenopausal women aged 50-74 years between 8 and 30 years after menopause, none taking oestrogen.
Measurements: Serum concentration of oestradiol, oestrone, and sex hormone binding globulin (SHBG) determined by immunoassay. Cognition assessed using the mini-mental state examination questionnaire (MMSE).
Results: In this group, 149 individuals had a MMSE score < 27, while only 89 individuals had a MMSE score < 26, indicating a relatively healthy population with regard to cognitive ability. Cognition decreased with age, time since menopause and blood pressure, and was better with higher age at menopause. Serum oestrogens and SHBG levels were not related to age, age at menopause, or time since menopause, and oestrogen levels were positively associated with blood pressure. After adjustment for mean arterial pressure and SHBG, the frequency of mild cognitive impairment decreased significantly with higher oestradiol and oestrone serum levels [ORs Q5 vs. Q1: 0.41 (95% CI 0.20-0.84) and 0.51 (95% CI 0.20-0.99) for oestradiol and oestrone, respectively].
Conclusions: Postmenopausal women with higher remaining circulating oestradiol levels appear less likely to suffer from cognitive impairment. This effect is independent of age at menopause, time since menopause and BMI. These findings support the hypothesis that endogenous oestrogens may protect against cognitive decline with ageing.