Scientists measuring the brain activity of more than 200 people found that female brains were more youthful than those of males of the same age.
In a study published on Monday in the Proceedings of the National Academy of Sciences, the researchers studied 205 people to figure out how their brains use a portion of sugar in a process called aerobic glycolysis that sustained brain development but dropped steadily with age. The participants took part in six studies across the Washington University School of Medicine.
All brains get smaller with age, and it was already known that men's tend to shrink at a faster rate.
The researchers found that if you compared a male and female brain of the same chronological age, the female brain will appear to be about three years younger, they say in a press release.
They found that metabolic brain ageing tracked chronological ageing in both men and women.
"The average difference in calculated brain age between men and women is significant and reproducible, but it is only a fraction of the difference between any two individuals", Goyal said. I think this could mean that the reason women don't experience as much cognitive decline in later years is because their brains are effectively younger, and we're now working on a study to confirm that'.
So in the new study, the researchers analyzed brain-imaging scans of 121 women and 84 men who ranged in age from 20 to 82.
The initial study was conducted by first training the machine learning algorithm using men's ages and brain metabolism data.
"It's not that men's brains age faster - they start adulthood about three years older than women, and that persists throughout life", Goyal said.
In the next stage of their research, the team will be trying to determine if cognitive problems occur less frequently in people with brains that seem younger.
Interestingly, the gap between men and women's brain ages was detectable even in young adults in their 20s.
Scientists hope to find out if metabolic differences in the brain may play a protective role for women, who tend to score better than men on cognitive tests of reason, memory and problem solving in old age.
More studies are now needed to better understand this brain-age difference and whether it affects the risk of age-related brain disease, such a Alzheimer's.