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. This could provide one clue to why women tend to stay mentally sharp longer than men, the authors noted.
"It's not that men's brains age faster", said scientist Dr. Manu Goyal from the Washington University School of Medicine. "It's possible the finding we're seeing helps to explain some of that". The brain still uses sugar for cognitive function, but aerobic glycolysis plateaus at a low level usually by the time people are in their 60s. The study's participants had PET scans done so the scientists could observe the flow of oxygen and glucose in their brains. Our recent multitracer PET brain imaging data demonstrate that as the brain ages, its resting metabolism gradually shifts away from a mixture of nonoxidative and oxidative use of glucose to predominantly oxidative metabolism (4, 5). The program did pretty well, but it made some mistakes, so the research team set about accounting for those errors.
People tested in the study ranged from 20 to 82 - and the relative youth of women's brains was seen in the young ones too. They suggest that developmental differences in men and women could play a role.
To ensure their data was on point, the researchers also used the same algorithm but in reverse, feeding first the women's data and then applying it to the men's. Doing it this way, the algorithm reported that the men's brains were about 2.4 years older than their actual chronological ages.
Also, the relative youthfulness of women's brains was detectable even among the youngest participants, who were in their 20s.
And Goyal says the team wondered whether this difference was more pronounced in men or women. Goyal, Raichle, Vlassenko and colleagues are now following a cohort of adults over time to see whether people with younger-looking brains are less likely to develop cognitive problems.More news: Ireland's Stander in Six Nations fitness battle
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The researchers suspect that women gain this advantage during puberty, Goyal said. Goyal said, "When we looked at males versus females, we did find an effect". In fact, it might go down and then come back up again. It calculated that the women were, on average, 3.8 years younger than they actually were.
Even so, for some people there was a big difference between their brain age and their chronological age. Having a younger brain for longer could make the brain more vulnerable to certain things as well.
"What we don't know is what it means".
The new research focused on metabolic processes that have a major influence on brain performance and ageing. Evolutionary theorists have predicted that females might have more youthful brains (neoteny) as compared with males, but until now findings in support of this theory have been limited to postmortem transcriptional analysis, some of which is contradictory. She was not part of the study.
There is no doubt that women and men are biologically quite different. The findings, available online the week of February 4 in Proceedings of the National Academy of Sciences, could be one clue to why women tend to stay mentally sharp longer than men.
Human brain aging is characterized by varying trajectories.