There's a widely held belief that women experience moodiness and fuzzy thinking because of the drop in estrogen during menopause. And women have looked to hormone replacement therapy for relief.
But researchers increasingly think there's not much of a link between declining levels of estrogen during menopause and cognition.
Scientists at Stanford University tested the memory and overall mental sharpness of 643 healthy postmenopausal women. They then measured the women's natural hormone levels. They were particularly interested in a type of estrogen called estradiol, which typically drops after menopause.
The scientists also divided the women into two groups: those who had gone into menopause within the last six years, and those who were more than 10 years past menopause. That's because it's been thought that taking supplemental estrogen shortly after menopause helps women stay sharp more than if they start later.
But in both younger and older postmenopausal women, higher estradiol levels didn't seem to affect cognition.
The findings were published in the Proceedings of the National Academy of Sciences.
"The findings imply that for younger women who are considering hormone therapy, there's no need to rush into it because of the belief that it's going to improve memory," Dr. Victor Henderson, a neurologist and the study's lead researcher, told Shots.
Henderson says the issue of fuzzy thinking during and post menopause has stumped researchers for years. While it's clear that some women experience haziness during the menopausal transition, research is less clear on whether menopause causes any long-term cognitive changes.
Though a few studies do suggest that menopause could be linked to a small amount of cognitive impairment, most recent research, Henderson says, haven't found any link.
Henderson's study could get us one step close to solving the puzzle. Still, it's no means the last word.
"I don't think the finding is surprising," says Dr. JoAnn Manson, a researcher at Harvard and Brigham and Women's Hospital. But, she tells Shots, "the results have to be interpreted cautiously."
Manson is a principal investigator with Women's Health Initiative, a long term national health study that found in 2002 that hormone replacement therapy didn't protect women from heart attacks and stroke after menopause. That research prompted many women to stop taking supplemental estrogen. But women still worry that not taking HRT means their brains aren't working so well.
While this new finding about estrogen and cognition seems to make sense, Mason says, this sort of observational study can only look at how hormone levels are associated with women's ability to think. It can't prove for sure that estrogen has no effect on the brain.
Another issue is that the study only looked at women's natural hormone levels. More research needs to be done before we can know for sure how supplemental estrogen affects women's mood and memory.
Henderson says he has already started looking at the effects of hormone supplements on the same group of women.
Copyright 2016 NPR. To see more, visit http://www.npr.org/.