Postmenopausal women not taking estrogen replacement therapy who underwent hysterectomy, either with or without removal of both ovaries (bilateral oophorectomy), had scores on cognitive function tests that were similar to women who had not had a hysterectomy. Also, use of estrogen replacement therapy did not improve the cognitive performance of women who had undergone hysterectomy, according to a study supported in part by the Agency for Healthcare Research and Quality (HS06726). This finding discounts the link between estrogen deficiency and age-related decline in cognitive function in older women, conclude Donna Kritz-Silverstein, Ph.D., and Elizabeth Barrett-Connor, M.D., of the University of California, San Diego.
The researchers analyzed data on a community-based sample of 885 postmenopausal women aged 60 to 89; subjects were white, middle to upper-middle class, and relatively well educated. The women, who had undergone a hysterectomy with or without ovary removal, completed 12 standardized tests of cognitive function. Overall, including those not currently using estrogen, there were no significant differences on mean cognitive function scores by hysterectomy and oophorectomy status, after adjustment for age, education, age at menopause, and past estrogen use. Among those currently using estrogen, women with a hysterectomy and bilateral oophorectomy performed less well on two tests of cognitive function. These differences, although statistically significant, were very small and unlikely to be of clinical significance.
The postmenopausal ovary continues to secrete testosterone, a hormone that has been associated with better cognitive performance. Although women with intact ovaries have reduced testosterone levels around the time of menopause, testosterone returns to premenopausal levels over time. After bilateral oophorectomy, older women have bioavailable testosterone levels that are 40 percent lower than those of intact women. However, testosterone levels may be further reduced in oophorectomized women receiving estrogen because estrogen increases sex hormone binding globulin, which binds preferentially to testosterone (making it less available). This may explain the insignificantly poorer performance of this group of women on two cognitive tests.
For more information, see "Hysterectomy, oophorectomy, and cognitive function in older women," by Drs. Kritz-Silverstein and Barrett-Connor, in the January 2002 Journal of the American Geriatrics Society 50, pp. 55-61.