Women’s brains appear three years younger than men’s in scans, study reveals

Scientists hope difference between sexes in 'metabolic age' may help explain why female brains are more resistant to memory loss as they get older

PET scans of 200 people's brains were used to measure their 'metabolic age' in a new study (Getty Images)

Women’s brains appear younger than those belonging to men of exactly the same age in scans measuring the organ's metabolism, according to a new study.

They were found to be around three to four years more “youthful” than their male contemporaries.

The discovery may help doctors understand why women are less susceptible to memory loss and neurological diseases as they age.

Brain ageing is known to be associated with a gradual decline in brain metabolism.

With their new study, scientists from Washington University in St Louis, Missouri. attempted to gauge the “metabolic age” of people’s brains in their new study.

In particular, they focused on a process known as aerobic glycolysis, which uses glucose sugar to sustain brain development as people grow from children to adults.

As adulthood progresses, less and less of the glucose pumped through people’s brains to provide them with energy is funnelled into this process. Only a tiny amount goes in by the time people are in their 60s.

The fraction of sugar powering glycolysis was therefore used by scientists in their new study as a marker of brain age.

They conducted positron emission tomography (PET) scans on 121 women and 84 men, which allowed them to measure oxygen and glucose as they flowed through their brains.

PET scans are imaging tests that allows doctors to check for diseases the body.

Taking this data, they fed it into a machine-learning algorithm and trained it to recognise brain age based on the metabolic information.

When training the algorithm using men’s ages and brain data before applying it to women, it concluded that female brains were aged an average of 3.8 years younger than their actual, chronological age.

One of the study's authors, Professor Manu Goyal, said this was a fairly strong example of measurable differences between sexes, although not as strong as more well-established distances like height.

Women’s brains known to be more resilient to cognitive decline, with older women tending to score higher in tests of reason, memory and problem solving than men of the same age.

Publishing their result in the journal Proceedings of the National Academy of Science, the scientists suggested that higher levels of youthful glycolysis were helping to promote women’s learning and brain development even into old age.

“We’re just starting to understand how various sex-related factors might affect the trajectory of brain aging and how that might influence the vulnerability of the brain to neurodegenerative diseases,” said Prof Goyal. “Brain metabolism might help us understand some of the differences we see between men and women as they age.”

People tested in the study ranged in age from 20 to 82, and surprisingly the relative youth of women’s brains was not only seen in the older subjects, but the young ones too.

This suggested that women start off with “younger” brains that have higher levels of glycolysis.

“It’s not that men’s brains age faster – they start adulthood about three years older than women, and that persists throughout life,” said Prof Goyal.

To explore how this theory plays out in practice, the research team is now following a group of adults over time to determine whether those with younger-looking brains are more resistant to declines in brain function.