Women whose ovaries were surgically removed before the age of 46 had a higher risk of mild cognitive impairment (MCI) around 30 years later, compared with those who did not undergo bilateral oophorectomy, according to a population-based linkage study published in JAMA Network Open.
The findings suggest that “physicians treating women with premenopausal bilateral oophorectomy need to be aware of their patients’ risk of cognitive impairment or MCI and should consider implementing treatment-monitoring plans,” noted lead author Walter A. Rocca, MD, MPH, from the division of epidemiology, department of quantitative health sciences, at the Mayo Clinic, Rochester, Minn. and colleagues.
The results may particularly “help women at mean risk levels of ovarian cancer to better evaluate the risk-to-benefit ratio of undergoing bilateral oophorectomy prior to spontaneous menopause for the prevention of ovarian cancer,” they emphasized.
While the link between premenopausal bilateral oophorectomy and higher risk of cognitive impairment has been previously suggested, this new study “contributes valuable new data to a major public health importance issue and addresses a number of important shortcomings of existing literature,” Marios K. Georgakis, MD, PhD, and Eleni T. Petridou, MD, PhD, noted in an accompanying commentary.
“As bilateral oophorectomy is still a common procedure at least in well-resourced countries, the results of these studies should alert clinicians about its potential public health consequences. Given that the abrupt cessation of ovarian hormones might be accompanied by previously underestimated long-term adverse effects, treating physicians proposing the operation should weigh its benefits against potential long-term harmful effects, especially among women without an absolute indication,” noted Dr. Georgakis and Dr. Petridou, respectively from the Center for Genomic Medicine at Massachusetts General Hospital in Boston and the National and Kapodistrian University of Athens.
The case-control cross-sectional study used data from the Mayo Clinic Study of Aging (MCSA), a prospective, population-based study examining risk factors for, as well as prevalence and incidence of cognitive decline and MCI among a representative sample of women in Olmsted County, Minn. It included 2,732 women aged 50-89 years who participated in the MCSA study from 2004 to 2019 and underwent a clinical evaluation and comprehensive cognitive testing including nine tests covering four cognitive domains. Almost all of the subjects (98.4%) were White. The mean age of cognitive evaluation was 74 years – at which time 283 women (10.4%) were diagnosed with MCI (197 with amnestic and 86 with nonamnestic MCI). Data from the Rochester Epidemiology Project medical record–linkage system showed a total of 625 women (22.9%) had a history of bilateral oophorectomy. Among this group, 161 women underwent the procedure both before age 46, and before menopause, with 46 (28.6%) receiving oral conjugated equine estrogen (unopposed) and the remaining 95 (59.0%) receiving no estrogen therapy.
The study found that, compared with women who did not undergo bilateral oophorectomy, those who did so before age 46, but not after this age, had statistically significantly increased odds of MCI (adjusted odds ratio, 2.21; P < .001). When type of MCI was examined, the risk was statistically significant for nonamnestic MCI (aOR, 2.96; P < .001), and amnestic (aOR, 1.87; P =.03). The study also found no evidence that estrogen therapy was associated with decreased risk of MCI among women aged less than 46 years, with an aOR of 2.56 in those who received estrogen therapy and 2.05 in those who did not (P = .01 for both).
Finally, in women who had bilateral oophorectomy before menopause and before age 50, surgical indication for the procedure affected the association with MCI. Indications of either cancer or “no ovarian condition” (i.e., performed at the time of hysterectomy) were associated with no increased risk, whereas there was a statistically significantly increased risk associated with benign indications such as an adnexal mass, cyst or endometriosis (aOR, 2.43; P = .003). “This is important,” noted the commentators, “because in many of those cases removal of both ovaries could be avoided.”
The study also found that, compared with women who had not undergone bilateral oophorectomy, those who had also had increased frequency of cardiovascular risk factors, heart disease, and stroke at the time of their cognitive evaluation. “Additional research is needed to clarify the biological explanation of the association,” the investigators said.
The prevailing hypothesis for why premenopausal bilateral oophorectomy is associated with cognitive decline “is that the abrupt endocrine cessation of exposure to ovarian hormones accelerates the aging process,” the commentators noted. “Most important from a clinical perspective is whether these women would benefit from specific hormone replacement therapy schemes. Observational studies cannot reliably answer this question, and possibly it is time to rethink designing trials in specific groups of women who underwent bilateral oophorectomy before 46 years of age starting treatment immediately thereafter.”
In an interview Dr. Georgakis elaborated on this point, saying that, while the Women’s Health Study clearly showed no benefit of hormone replacement therapy for preventing dementia, it recruited women who were aged 65 years or older and had therefore undergone menopause more than 10-15 years earlier. “A hypothesis suggests that a critical vulnerability window exists shortly after menopause during which hormone replacement therapy might be needed to ameliorate any elevated risk,” he said. “Thus, it might make sense to reconsider a trial focused on this group of premenopausal women, who need to undergo oophorectomy at a young age (<46 years). Early initiation would be important. Unfortunately, such a trial would be difficult to conduct, because these women would need to be followed up for very long periods, as cognitive decline usually does not occur before the age of 65.”
Asked to comment on the study, Meadow Good, DO, an ob.gyn., female pelvic medicine and reconstructive surgeon, and physician adviser for Winnie Palmer Hospital for Women & Babies in Orlando, said this study adds credibility to previous studies showing the cognitive risk associated with premenopausal bilateral oophorectomy. “The literature is now pointing to a need to refrain from elective bilateral oophorectomy in women less than 60,” she said in an interview. “It should not be common that a women receives a bilateral oophorectomy before 60 for benign reasons.”
She added that cognition is not the only think at stake. “Bilateral oophorectomy before the age of 60 has a higher risk of incident heart disease, stroke, lung cancer and total cancers,” she said, citing a prospective cohort study within the Nurses’ Health Study.
Dr. Rocca reported financial support from the Mayo Clinic Research Committee during the conduct of the study. One coauthor reported unrestricted grants from Biogen and consulting fees from Brain Protection outside the submitted work. No other disclosures were reported from the authors. Dr. Georgakis, Dr. Petridou, and Dr. Good reported no conflicts of interest. The study was funded by the National Institute on Aging. It also used resources of the Rochester Epidemiology Project medical record–linkage system, which is supported by the NIA, the Mayo Clinic Research Committee, and user fees. Dr. Rocca was partly funded by the Ralph S. and Beverley E. Caulkins Professorship of Neurodegenerative Diseases Research of the Mayo Clinic.