Adult men have larger brains than women. The difference was measured at approximately 10% on average. During aging, however, the male brain loses volume more rapidly than the female brain.
Brain atrophy is a normal phenomenon with age. It generally begins after the age of 60. A study published in the journal Pnas (Proceedings of the National Academy of Sciences) and coordinated by the universities of Sydney and Oslo measured the different speed with which this process occurs in the two sexes.
In an area of the cerebral cortex that has the task of processing the sensations of touch, temperature and pain, the position of the body and its movements, for example, the volume is reduced by 1.2% per year in women and by 2% in men.
“Men show decline in more brain regions, including many areas of the cortex“, the neuroscientists wrote. “In women the reduction in volume affected fewer regions and was more limited in the cortex.”
The researchers enrolled almost 5 thousand volunteers and subjected them to various head MRIs, three or more years apart from each other. The individuals studied were free of cognitive problems, despite the reduction in volume due to the passing of the years.
Own The lack of a link between brain size and dementia has amazed researchers. In fact, their goal was to understand whether atrophy was an indicator of the risk of getting Alzheimer’s disease.
Since this disease affects females in two-thirds of cases, and since it is linked to advanced age, neuroscientists expected a result opposite to what they found. “If the female brain had shown a faster reduction in volume than the male brain, this would have helped us explain the higher prevalence of Alzheimer’s,” explained one of the co-authors, Anne Ravndal from the University of Oslo.
Many neurological diseases affect the sexes differently. Autism, dyslexia, attention deficit and hyperactivity are, for example, typical problems of the male sex, while that of fFemales are more often affected by depression, anxiety and anorexia. So far, however, the relationship with the structural differences in the brain between the sexes has eluded researchers.
The same difference in volume between men and women at a young age is not linked to a different IQ. Its value is highly variable between individuals, but independently of sex.
If intelligence depended only on volume, today we would be less gifted A wise man lived 100 thousand years agogiven that for mysterious reasons our brain has shrunk by 13% compared to then.
Today not even an expert would be able to distinguish a male brain from a female one with the naked eye. The first to do so, in 2024, in an experiment conducted by New York University and published in Scientific Reportswas an artificial intelligence model trained to recognize tiny details in head MRIs.
A study also released this week on Science Translational Medicinehowever, conducted on mice, suggests a different path from that of the volume to explain the greater spread of Alzheimer’s in women. Researchers at the University of California – Los Angeles have observed a gene on the X chromosome responsible for a high level of inflammation in particular brain cellsthose of the microglia, which perform the immune defense function. Because women have a double copy of the X chromosome, the activity of the gene that promotes inflammation is double that of men.
Inflammation of brain tissues plays a deleterious role in aging, the onset of Alzheimer’s and multiple sclerosis. This last disease is also much more common in females, with a ratio of three to one.
