Association of Premenopausal Bilateral Oophorectomy With Cognitive Performance and Risk of Mild Cognitive Impairment

IMPORTANCE: The associations of bilateral oophorectomy among premenopausal women, age at oophorectomy, and use of estrogen therapy after oophorectomy with cognitive performance later in life remain controversial. OBJECTIVE: To investigate whether women who underwent premenopausal bilateral oophorectomy were at increased risk of mild cognitive impairment (MCI) and experienced decreased global or domain-specific cognitive performance. DESIGN, SETTING, AND PARTICIPANTS: This case-control study and cross-sectional study were made possible by combining data from the Mayo Clinic Study of Aging (MCSA) and the Rochester Epidemiology Project (REP) medical record–linkage system. The studies were conducted among a population-based sample in Olmsted County, Minnesota, consisting of 2732 women aged 50 to 89 years who participated in the MCSA study from 2004 to 2019 and underwent a clinical evaluation and comprehensive cognitive testing. Data were analyzed from January to May 2021. EXPOSURES: Medical record documentation of bilateral oophorectomy abstracted from a medical record–linkage system (ie, REP). MAIN OUTCOMES AND MEASURES: Odds of MCI and global or domain-specific z scores on cognitive tests were measured at the first MCSA visit. The median (IQR) lag time between bilateral oophorectomy performed before menopause and before age 50 years and cognitive evaluation was 30 (22-38) years. RESULTS: Among 2732 women aged 50 to 89 years (median [IQR] age at evaluation, 74 [66-81] years) who participated in the MCSA, the case-control study included 283 women with MCI (10.4%) and 2449 women without cognitive impairment (89.6%). Bilateral oophorectomy before menopause and before age 46 years was associated with clinically diagnosed MCI (adjusted odds ratio [aOR], 2.21; 95% CI, 1.41-3.45; P < .001) compared with no bilateral oophorectomy. The presence of an association with MCI varied by surgical indication, with an association among 259 women with bilateral oophorectomy before menopause and before age 50 years for the indication of benign ovarian condition (aOR, 2.43; 95% CI, 1.36-4.33; P = .003) but not for cancer or no ovarian condition. The presence of an association did not vary by estrogen therapy after bilateral oophorectomy, with associations among women aged less than 46 years with estrogen therapy (aOR, 2.56; 95% CI, 1.24-5.31; P = .01) and without estrogen therapy (aOR, 2.05; 95% CI, 1.18-3.52; P = .01). The cross-sectional study included 625 women with a history of bilateral oophorectomy (median [IQR] age, 75 [70-82] years) and 2107 women without a history of bilateral oophorectomy (median [IQR] age, 73 [65-80] years). Premenopausal bilateral oophorectomy was performed before age 46 years among 161 women and was associated with decreased global cognition z score (β, −0.17; 95% CI, −0.32 to −0.03; P = .02), attention and executive domain z score (β, −0.21; 95% CI, −0.36 to −0.05; P = .009), and Short Test of Mental Status score (β, −0.51; 95% CI, −0.95 to −0.08; P = .02) compared with no bilateral oophorectomy. CONCLUSIONS AND RELEVANCE: This study found that women who underwent bilateral oophorectomy before menopause had increased odds of MCI and poorer performance on cognitive tests approximately 30 years later compared with women who did not undergo bilateral oophorectomy.