Women’s brains are effectively several years younger than brains of men the same biological age, according to new research published in the Proceedings of the National Academy of Sciences. While all human brains shrink as their owners get older, male brains degenerate at a much faster rate than female brains, which may not only explain why grandma is a bit sharper than grandpa, but also a number of other gender differences that seem to be exacerbated by cognitive decline.
“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 study co-author Manu Goyal, Assistant Professor of Radiology and Neurology at Washington University School of Medicine in St. Louis, in a statement. “Brain metabolism might help us understand some of the differences we see between men and women as they age.”
Brain metabolism helps scientists understand how people age neurologically because the way the brain processes sugar changes with age. While babies and children burn through glucose to help their brains grow and develop, less sugar is used for this purpose as people mature. There’s evidence that women’s brains are less vulnerable to age-related stressors than men, but until the current study it has been unclear if gender differences in brain metabolism have anything to do with that.
To learn more about this, Goyal and his colleagues measured the glucose consumption and flow of oxygen in the brains of about 200 men and women. To determine each person’s “brain age” relative to their chronological age, researchers trained a machine-learning algorithm to identify the relationship between age and average brain metabolism. The algorithm revealed that women’s brains were 3.8 years younger than their chronological ages. Men’s brains were 2.4 years older.
Not that that’s anything to write home about. “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. “It is stronger than many sex differences that have been reported, but it’s nowhere near as big a difference as some sex differences, such as height.”
But the results are consistent with data indicating that older women tend to score better on tests of reason, memory, and problem solving compared to men of the same age. Differences in how their brains use glucose may help to explain why, and follow up research might help scientists close the gender gap when it comes to cognitive decline.
“It’s not that men’s brains age faster – they start adulthood about three years older than women, and that persists throughout life,” Goyal added. “What we don’t know is what it means. 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 currently working on a study to confirm that.”