MONDAY, Feb. 4, 2019 (HealthDay News) -- "Boys will be boys" goes the old saying, but girls might have the last laugh.

It turns out that female brains tend to age more slowly, researchers report.

On average, women's brains appear to be about three years younger than those of men at the same chronological age. This could provide one clue to why women tend to stay mentally sharp longer than men, the authors noted.

"Women tend to score better on cognitive tests than men as they age," said lead researcher Dr. Manu Goyal, an assistant professor at the Mallinckrodt Institute of Radiology at Washington University School of Medicine in St. Louis. "It's possible the finding we're seeing helps to explain some of that."

Scientists have observed that people's brains change both in structure and function as they grow older.

One change involves the way the brain uses sugar and oxygen to fuel its efforts, Goyal said.

"The brain really relies on glucose and oxygen to meet its metabolic needs, and it's a very large consumer of those resources," Goyal said. "How it uses glucose and oxygen, and in what parts of the brain it uses the most, changes as people typically age."

Goyal and his colleagues initially set out to see if a computer program could use this brain metabolism pattern to predict someone's age. The program did pretty well, but it made some mistakes, so the research team set about accounting for those errors.

The researchers recruited 205 people aged 20 to 82 to undergo brain imaging scans that measured the flow of oxygen and sugar within their brains. That data was then fed into the computer program.

"One of the things we looked at was women versus men. When we started looking at that, we were pleasantly surprised that when the machine was trying to age a woman compared to a man, it consistently aged the woman to be a little bit younger than the man," Goyal said.

"On average, it found that women appeared to be younger than men in terms of their metabolic brain age, in terms of what their brain metabolism pattern looked like," he said.