In an analysis of data from a prospective study, there were no significant associations between estrogen levels and cognition among postmenopausal women, Victor Henderson, MD, of Stanford University in Stanford, Calif., and colleagues reported online in the Proceedings of the National Academy of Sciences.
There was no relationship between the hormone and brain function whether women were newly postmenopausal, or if they'd been postmenopausal for at least 10 years.
Progesterone, however, did appear to be related to verbal memory and global cognition among women who were newly postmenopausal, the researchers found.
Henderson said in a statement that the findings don't "necessarily mean that estrogens are irrelevant to cognition, since we have no way of measuring estrogen directly at the brain level. But they imply that boosting blood levels of estradiol or estrone -- even in younger postmenopausal women -- may not have a substantial effect on cognitive skills one way or the other."
He added that the progesterone finding hasn't been previously reported and needs further confirmation.
Henderson and colleagues looked at data on 643 healthy postmenopausal women who were part of the Early Versus Late Intervention Trial with Estradiol (ELITE) study.
The women ranged in age from 41 to 84 and none were on hormone therapy. They were assessed in two categories: those who had started menopause less than 6 years ago, and those who started more than 10 years ago.
The researchers conducted neuropsychological tests to gauge memory and cognition, and screened for various hormone levels: estradiol, estrone, progesterone, testosterone, and sex hormone-binding globulin.
Overall, they found no significant relationship between estradiol or estrone and tests of verbal memory, executive function, or global cognition. And those results didn't differ between the two groups, whether the women were in early or late postmenopause.
Levels of progesterone, however, appeared to be tied to verbal memory and global cognition among women who were in early postmenopause. The higher the levels of progesterone, they reported, the better the outcomes on tests of verbal memory and global cognition in these younger women.
"We found that serum [progesterone] was positively related to verbal memory and global cognition in postmenopausal women closer to menopause," the researchers wrote.
They also found that sex hormone-binding globulin was associated with verbal memory, with similar effects in both groups.
But none of the hormones had any relationship to mood or depression, they noted.
Although Henderson and colleagues cautioned that hormone blood levels may not reflect concentrations in the brain, they still concluded that their study was not in line with earlier findings that estrogen levels are related to cognition. They added that the new finding regarding progesterone levels and cognition needs to be confirmed.
The research was supported by grants from the NIH and Robert E. and May R. Wright Foundation.
The researchers reported no conflicts of interest.