Scans Show Female Brains Remain Youthful As Male Brains Wind Down

Feb 4, 2019
Originally published on February 8, 2019 3:52 pm

Women tend to have more youthful brains than their male counterparts — at least when it comes to metabolism.

While age reduces the metabolism of all brains, women retain a higher rate throughout the lifespan, researchers reported Monday in the journal Proceedings of the National Academy of Sciences.

"Females had a younger brain age relative to males," says Dr. Manu Goyal, an assistant professor of radiology and neurology at Washington University School of Medicine in St. Louis. And that may mean women are better equipped to learn and be creative in later life, he says.

The finding is "great news for many women," says Roberta Diaz Brinton, who wasn't connected with the study and directs the Center for Innovation in Brain Science at the University of Arizona Health Sciences. But she cautions that even though women's brain metabolism is higher overall, some women's brains experience a dramatic metabolic decline around menopause, leaving them vulnerable to Alzheimer's.

The study came after Goyal and a team of researchers studied the brain scans of 205 people whose ages ranged from 20 to 82. Positron emission tomography scans of these people assessed metabolism by measuring how much oxygen and glucose was being used at many different locations in the brain.

The team initially hoped to use the metabolic information to predict a person's age. So they had a computer study how metabolism changed in both men and women.

Then they reversed the process and had the computer estimate a person's age based on brain metabolism data.

The approach worked. "It was highly predictive of age," Goyal says.

Even so, for some people there was a big difference between their brain age and their chronological age. And Goyal says the team wondered whether this difference was more pronounced in men or women.

So they checked.

"When we looked at males vs. females, we did find an effect," Goyal says. "We found in fact that females had a younger brain age relative to males."

Women's brains appeared about four years younger, on average. But it's still not clear why.

"It makes us wonder, are hormones involved in brain metabolism and how it ages?" Goyal says. Or is it something else, like genetics?

Whatever the cause, higher metabolism may give female brains an edge when it comes to learning and creativity in later life, Goyal says.

"But it might also set up the brain for certain vulnerabilities," he says, including a higher risk of developing Alzheimer's disease.

Brinton sees it differently. She thinks women's higher brain metabolism protects them from Alzheimer's when they are young.

But menopause, she says, causes an "energy transition in the brain," one that affects the brain metabolism of some women far more than others.

Brinton's research suggests that the women most likely to experience a dramatic drop are those who carry a gene variant called APOE4, which increases a person's risk of developing Alzheimer's, or those who have risk factors for Type 2 diabetes.

"It's those women who will begin to develop the pathology of Alzheimer's disease earlier," she says.

As brain metabolism decreases in these women, Brinton says, there's an increase in the sticky proteins that are associated with Alzheimer's.

"This is a process that starts very early in the aging process for some women," Brinton says. "And we can intervene."

How? The steps are a lot like those intended to prevent diabetes, Brinton says. They include diet, exercise and drugs that help the brain and body metabolize sugar.

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ARI SHAPIRO, HOST:

A new study published today in the Proceedings of the National Academy of Sciences says a woman's brain tends to remain youthful long after a man's brain has started to slow down. NPR's Jon Hamilton reports.

JON HAMILTON, BYLINE: A person in their 60s may have the body of someone much younger. And scientists at Washington University in St. Louis thought the same thing might be true of a person's brain. So they studied the brains of more than 200 adults. Special scans revealed each brain's metabolism, something that decreases with age. Manu Goyal a neuroradiologist says the team was hoping...

MANU GOYAL: We could perhaps predict the age of the brain using that metabolic information.

HAMILTON: The scientists had a computer study how metabolism changed with age. Then they reversed the process and had the computer estimate a person's age using information on brain metabolism. And Goyal says the approach worked.

GOYAL: It's quite accurate. It's about maybe 90 percent accurate.

HAMILTON: Even so, for some people, there was a big difference between their brain age and their chronological age. And Goyal says the team wondered whether this difference was more pronounced in men or women.

GOYAL: When we looked at sex, when we looked at males versus females, we found in fact that females had a younger brain age relative to males.

HAMILTON: About four years younger on average. Goyal says it's not clear why women's brains remain youthful.

GOYAL: It makes us wonder, are hormones involved in influencing brain metabolism and how it ages?

HAMILTON: Or is it something else, like genetics? Goyal says higher metabolism may give female brains an edge when it comes to learning and creativity in later life. But he says all that youthful vigor also could have a downside.

GOYAL: It might also set up the brain for certain vulnerabilities.

HAMILTON: Like Alzheimer's disease. But Roberta Diaz Brinton, who studies brain aging at the University of Arizona, has a more optimistic take on the results.

ROBERTA DIAZ BRINTON: It's great news for many women.

HAMILTON: Brinton says the great news is for the majority of women whose brain metabolism remains high as they age. Her research shows these women have a low risk of developing Alzheimer's. But Brinton says around menopause, a small proportion of women experience a dramatic drop in brain metabolism.

BRINTON: This transition is actually an energy transition in the brain.

HAMILTON: Brinton says women who develop metabolic problems tend to carry a gene that increases the risk for Alzheimer's. They're also at risk for Type 2 diabetes.

BRINTON: It's those women who will begin to develop the pathology of Alzheimer's disease earlier.

HAMILTON: Brinton says as brain metabolism decreases in these women, there's an increase in the clumps of sticky protein associated with Alzheimer's.

BRINTON: This is a process that starts very early in the aging process in some women, and we can intervene.

HAMILTON: How? Brinton says it's a lot like preventing diabetes. The key is diet, exercise and drugs that help the body and brain metabolize sugar. Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.