Researchers say men’s brains start out adulthood as “older” and never catch up as they age.
Men and women have significant physical differences: shape, appearance, sex organs.
They also have less obvious differences: One sex is often more at risk for certain health conditions or diseases.
Now, researchers say men and women have another unseen but significant difference: their brain age.
According to new research from the Washington University School of Medicine in St. Louis, women’s brains appear to be on average three years younger than the brains of men of the same chronological age.
That difference is present from young adulthood through senior years, which means women’s brains also age more slowly than men’s brains.
The human brain tends to shrink with age. Brains also change how they make and use the primary source of energy, which is a type of sugar called glucose.
The changes may happen to men and women equally, but men’s brains start at a disadvantage and remain metabolically older than women’s brains throughout their lives, despite any age-related shifts.
To find these differences, the researchers recruited more than 200 adults, ages 20 to 82, to take part in a series of PET scans.
These imaging tests helped the study authors measure the flow of oxygen and glucose in the brains.
They also looked at the level of aerobic glycolysis, a process by which the brain converts glucose to energy. Younger brains have higher levels of aerobic glycolysis. That number dips as people age.
They then took the men’s brain measurements and fed them to a machine-learning algorithm they created for this study. The computer then developed a relationship between the men’s brain age and their brain’s metabolic data.
When they fed the women’s brain metabolism data to the algorithm, the program found that, on average, female brains were 3.8 years younger than male brains.
When they did the experiment in reverse, first teaching the algorithm with women’s data, then using the men’s data, the difference shrank, but men’s brains still remained 2.4 years older than their true ages.
These differences were also observed in the youngest participants. That means males enter adulthood with a brain that is metabolically older and it never catches up to women’s younger brains.
It’s unclear so far if there is significance to having a younger brain.
This research is a first of its kind and the authors of the study are only beginning to explore what they might use this data to understand and predict.
“It’s not that men’s brains age faster. They start adulthood about three years older than women and that persists throughout life,” says Dr. Manu Goyal, an assistant professor of radiology at Washington University’s Mallinckrodt Institute of Radiology and an assistant professor of neurology and of neuroscience. “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.”
The study, which was published in the Proceedings of the National Academy of Sciences of the United States of America, is seen as an important step toward understanding gender differences in health and medicine.
“This study theorizes that factors that influence brain development, including sexual differences, and exposure to different hormonal, inflammatory, and immunological environments during development, might be very important in determining how brain aging actually plays out,” says Dr. Verna R. Porter, a neurologist and director of the Alzheimer’s disease program at Providence Saint John’s Health Center in California.
Porter notes that differences, such as hormonal exposure, between males and females may influence the brain’s structural development. That could affect blood flow and eventually brain health during early adulthood.
It may also be, she adds, that these differences help the female brain stay more youthful and experience fewer age-related changes.
“This observation is in keeping with other studies that have suggested that the female brain experiences less loss of cerebral blood flow following puberty, more brain glycolysis during young adulthood, and less loss of protein synthesis-related gene expression during aging,” Porter told Healthline.
However, it’s important to note that while women have younger metabolic brain age, it is unclear if it has any protective effects on women’s brains in the long run.
Take for example the rates of Alzheimer’s disease.
While this study looked at people who were cognitively normal (that is, their brains showed no signs of impairment, plaque growth, or disease), the results may open a field of research that could improve the understanding of brain health and disease development.
Men and women alike can take steps to improve their brain health.
The exact difference those changes might have is not yet understood or quantified, however.
“It remains to be seen whether factors, such as diet, lifestyle, and exercise, may have the ability to change the relative age of the brain and therefore lead to increased brain resilience during aging,” Porter said.
However, Shannon L. Risacher, PhD, an assistant professor of radiology and imaging studies at the Indiana University School of Medicine and a radiologist at IU Health, suggests that it’s still worth making these brain-boosting lifestyle changes.
She told Healthline that these lifestyle choices are healthy for more than just your brain. They can significantly improve your overall health.
Eat a brain-healthy and heart-healthy diet: “It’s different from person to person, but having a good vascular system makes a big difference in how your brain functions. A lot of the things people are told to do to improve vascular problems, such as having a healthy diet that is low in bad fats and high in good fats, or a Mediterranean-style diet, can help vascular health,” Risacher said.
Get moving: “You don’t have to be a super athlete, but keeping yourself physically fit so your cells can process glucose well is important,” Risacher said. She adds that exercise also increases your oxygen intake, which is important for proper brain function.
Stay engaged: It’s not clear what effect puzzles, quizzes, and other types of brain activities can have on your overall brain health, but they may be helpful. “So far, the science does bear out that there is some beneficial effect,” Risacher said. “As long as they aren’t difficult to do and don’t frustrate you, they may be helpful.”
Spend time with friends: Risacher says the same research that says brain activities may be useful for improving brain health also show that people who remain socially active and keep a wide social network are also likely to experience less cognitive decline. It’s not clear which comes first — the social networks or the brain-engaging activities — but people who do both have slower progression.
Women’s brains are metabolically younger than men’s brains by up to three years.
That age gap doesn’t change with age, which suggests men’s brains start out older and don’t make up the difference.
However, there are things men (and women) can do to help their brain be healthier and less susceptible to cognitive decline.
A healthy diet, regular exercise, and staying engaged with a supportive social circle and brain-boosting activities may bolster brain health.