A new study by scholars at the School of Medicine at Washington University in St. Louis has found that women’s brains appear to be about three years younger than men’s of the same chronological age, metabolically speaking. The researchers believe these findings could be one clue to why women tend to stay mentally sharp longer than men.
The brain runs on sugar, but how the brain uses sugar changes as people get older. Younger people use a majority of their brain fuel for a process called aerobic glycolysis that sustains brain development and maturation. As people age, the fraction of brain fuel used for aerobic glycolysis drops steadily and levels off at very low amount by the time people are in their 60s.
For this study, 205 participants underwent PET scans to measure the flow of oxygen and glucose in their brains. For each person, the researchers determined the fraction of sugar committed to aerobic glycolysis in various regions of the brain. They trained a machine-learning algorithm to find a relationship between age and brain metabolism by feeding it the men’s ages and brain metabolism data. Then, the researchers entered women’s brain metabolism data into the algorithm and directed the program to calculate each woman’s brain age from its metabolism. The algorithm yielded brain ages an average of 3.8 years younger than the women’s chronological ages. They also performed the analysis in reverse by training the algorithm on women’s data and applied it to men’s. This time, the algorithm reported that men’s brains were 2.4 years older than their true ages.
“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 senior author Dr. Manu Goyal, an assistant professor of radiology at the university’s Mallinckrodt Institute of Radiology. “Brain metabolism might help us understand some of the differences we see between men and women as they age.”
For future studies, the researchers want to figure out why this phenomena exists and whether people with younger-looking brains are less likely to develop cognitive problems.
“What we don’t know is what it means,” said Dr. Goyal “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.”
The full study, “Persistent Metabolic Youth in the Aging Female Brain,” was published in the Proceedings of the National Academy of Sciences. It may be accessed here.