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 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 flushes, 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.
"This study fails to confirm the timing hypothesis," said study author Dr Victor W. Henderson of Stanford University School of Medicine in California and a Fellow of the American Academy of Neurology. "Our results suggest that healthy women at all stages after menopause should not take estrogen to improve memory. At the same time, women need not particularly be concerned about negative effects of postmenopausal estrogen supplements on memory when used for less than five years."
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.