Scientists might have found the reason why women tend to remain mentally sharp in old age compared to men: their brains are aging slightly later.

In a recent study, a team from the Washington University School of Medicine in St. Louis revealed that the brains of women and men age differently. This implies that sex might affect a person's risk of developing neurodegenerative diseases like Alzheimer's.

The findings were published in the Proceedings of the National Academy of Sciences on Monday, Feb. 4.

Different Brain Age

The human brain changes and deteriorate with age. As an individual grows older, the brain's metabolism slows down.

However, women and men experience the process a little differently. Researchers analyzed the brains of 205 people composed of 121 women and 84 men ages 20 to 82 years. Each of the participants underwent PET scans to measure the flow of oxygen and glucose.

To sort through the data, the researchers used machine learning to calculate each of the participants' brain age based on their metabolism. They found that on average, women's brains are 3.8 years younger than men's.

The researchers revealed that even in young people, their findings are the same. Even among the youngest participants, women's brains are younger than men's.

The team also performed the test in reverse. They found that on average, men's brains are 2.4 older than their chronological age.

"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," stated Manu Goyal, an assistant professor of radiology at the Washington University's Mallinckrodt Institute of Radiology. "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."

Study Implication

Goyal clarified that the study does not imply that men's brains are aging faster. In fact, the findings are not entirely surprising because it has been known that men start adulthood about three years older than women and apparently, this persists throughout their entire lives.

"What we don't know is what it means," he added. "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."

Samuel Neal Lockhart, an assistant professor at the Wake Forest School of Medicine who is not involved in the study, told CNN in an e-mail that the findings can help scientists understand how sex contributes to the decline of metabolic brain health later in life. He said that the study could add to the ongoing efforts to uncover the causes and early signs of Alzheimer's Disease.