Women’s brains appear to be aboutthree years younger than men’s of the same chronological age, metabolicallyspeaking, according to a new study.
The findings,according to the Proceedings of The National Academy of Sciences, could be oneclue to why women tend to stay mentally sharp longer than men.
Manu Goyal an authorand a professor of radiology says, “We’re just starting to understand howvarious sex-related factors might affect the trajectory of brain aging and howthat might influence the vulnerability of the brain to neurodegenerativediseases. Brain metabolism might help us understand some of the differences wesee between men and women as they age.”
The brain runs onsugar, but how the brain uses sugar changes as people grow and age. Babies andchildren use some of their brain fuel in a process called aerobic glycolysisthat sustains brain development and maturation. The rest of the sugar is burnedto power the day-to-day tasks of thinking and doing.
In adolescents andyoung adults, a considerable portion of brain sugar is also devoted to aerobicglycolysis, but the fraction drops steadily with age, leveling off at very lowamounts by the time people are in their 60s.
But researchers haveunderstood little about how brain metabolism differs between men and women. SoGoyal and colleagues studied 205 people to figure out how their brains usesugar.
The study consists of 121 women and 84 men, ranging in age from 20 to 82 years underwent PET scans to measure the flow of oxygen and glucose in their brains. For each person, the researchers determined the fraction of sugar committed to aerobic glycolysis in various regions of the brain. They trained a Machine Learning Algorithm to find a relationship between age and brain metabolism by feeding it the men’s ages and brain metabolism data.
Then, the researchersentered women’s brain metabolism data into the algorithm and directed theprogram to calculate each woman’s brain age from its metabolism. The algorithmyielded brain ages an average of 3.8 years younger than the women’schronological ages.
The researchers also performedthe analysis in reverse: They trained the algorithm on women’s data and appliedit to men’s. This time, the algorithm reported that men’s brains were 2.4 yearsolder than their true ages.
“The averagedifference in calculated brain age between men and women is significant andreproducible, but it is only a fraction of the difference between any twoindividuals,” Goyal says.
“It is stronger thanmany sex differences that have been reported, but it’s nowhere near as big adifference as some sex differences, such as height.”
The relativeyouthfulness of women’s brains was detectable even among the youngestparticipants, who were in their 20s.
“It’s not that men’sbrains age faster they start adulthood about three years older than women, andthat persists throughout life,” says Goyal, who is also an assistant professorof neurology and of neuroscience.
“What we don’t know iswhat it means. I think this could mean that the reason women don’t experienceas much cognitive decline in later years is because their brains areeffectively younger, and we’re currently working on a study to confirm that.”
Older women tend to score better than men of the same age on tests of reason, memory and problem-solving. The researchers are now following a cohort of adults over time to see whether people with younger-looking brains are less likely to develop cognitive problems.