So maybe that headline needs a bit of clarification: This new research has to do with postmenopausal women and their levels of estrogen. (Still, if you're a pre-menopausal woman, you should read this, too. Men, if you know any women, please read on.)
After a woman goes through menopause, her estrogen levels drop. This study, led by a Stanford School of Medicine researcher, was the first to look at associations between estrogen decline and cognition — both in women who went through menopause more recently (less than 6 years) and longer ago (more than 10 years). The research team wanted to know if the time from menopause made a difference in cognitive ability. And so we return to the headline: They found no connection.
"There were no differences between women close to the time of menopause and further from the time of menopause," said Stanford neurologist Victor Henderson, lead author of the study. The women were given a battery of neurological tests, not just "a short screening instrument," the authors wrote.
Primarily, the researchers looked at memory. "But we also looked at global cognition and executive function," Henderson said. "And based on relation to blood levels [of estrogen], we didn't find any important effects one way or the other."
Together with colleagues at the University of Southern California, Henderson looked at 643 women, none of whom have taken hormone replacement. While researchers did not find any connections between estrogen levels and cognition, they did uncover a surprising association between a different sex hormone, progesterone, and memory. In younger women, higher progesterone levels were associated with better memory.
Henderson stressed this finding was new and needed additional research before it can be confirmed.
In addition, Henderson drew a distinction between this research and what might happen in women who have Alzheimer's Disease.
"This study didn't look directly at Alzheimer's Disease," Henderson said, which is a "complex illness. … The biochemical changes that occur in Alzheimer's Disease differ from those that occur in usual aging."
In this study, the researchers were interested in the so-called "critical-window" theory. Henderson says that's the belief that estrogen can have different effects on health outcomes and those effects would differ depending on timing in relation to menopause.
For example, it is well-known, Henderson says, that hormone therapy in women over age 65 increases their risk of heart disease — but before age 65, hormone therapy does not bear risks and "might convey a small benefit," he said.
Researchers had wondered if the same could be true with cognition. The answer, again, is no. "Our findings don't support the critical-window hypothesis with regard to cognitive outcomes," he said.
Next, researchers will look at post-menopausal women who are taking hormone therapy to see if there are any effects from that treatment. But because this trial did not show effects, Henderson doubts there will be effects for women with the higher estrogen levels that will come by taking estrogen replacement.
"But until we look at the higher exposure directly, we don't know the answer to that," Henderson cautioned.
The findings were published Monday in the Proceedings of the National Academy of Sciences.