Contrary to popular belief, taking estrogen after menopause may not affect the memory and thinking abilities of healthy women no matter when the treatment is started.
The research is published in the July 20, 2016, online issue of Neurology, the medical journal of the American Academy of Neurology. The recent study is among the first large, long-term clinical trial to examine the cognitive effects of estradiol, a type of estrogen, on women both close to and long after menopause.
Millions of women take estrogen to treat hot flashes, night sweats and other symptoms caused by menopause. Estradiol is the main type of estrogen produced by women in their reproductive years. Previously, researchers thought estradiol benefitted memory and thinking in women soon after menopause but not later, called the “timing hypothesis.” Prior studies testing the theory have not found consistent results.
Now, researchers found no change in mental ability associated with estrogen therapy among women who used it after menopause, no matter when they started taking it.
For the study, 567 healthy women between the ages of 41 and 84 were classified into early and late groups. The early group was within six years of menopause and the late group was at least 10 years postmenopausal. Participants took beta-estradiol every day or a placebo pill. The women also used a progesterone vaginal gel or placebo gel, unless they had a hysterectomy. The average treatment duration was nearly five years. Cognitive tests were performed at the beginning of the trial, 2.5 years and five years to measure thinking skills including verbal memory.
Compared with starting scores on memory tests, women improved in verbal memory with practice, with and without hormone therapy, the study authors said. Scores were the same for those with and without hot flashes, and for women who had a uterus or had a hysterectomy.
"There is no important benefit, there is no important risk cognitively associated with the use of hormone therapy over at least five years," said lead researcher Dr. Victor Henderson. He is a professor of health research and policy, and neurology and neurological science at Stanford University School of Medicine, in Palo Alto, Calif.
"If a postmenopausal woman is considering taking hormone therapy with the thought that it might improve memory or other aspects of cognition, she should know that there is no evidence that it does benefit cognition," he said.
When starting hormone therapy, women should be given the smallest dose and for the shortest time possible, because of the increased risk of heart attack and breast cancer, Wu said.