Alzheimer's disease is unfair to women: according to InsermOf 25 patients, 15 were women compared to only 10 men. Since this disease is associated with aging (its risk increases from age 65 and skyrockets after age 80), a possible explanation for this apparent disparity could be that men age more rapidly in the brain, thus protecting them against the disease. To test this hypothesis, researchers from the University of Oslo (Norway) studied normal brain aging in men and women. Their research, published on October 13, 2025, in the journal PNAS, shows that, on the contrary, women's performance is much better than men's!
Men's brains generally age faster than women's brains.
To observe the natural evolution of the brain with age, researchers analyzed brain imaging of nearly 5,000 adults (2,181 men and 2,545 women), aged 17 to 95, all in good cognitive health. Each image was examined in detail, evaluating a total of 87 indices, including the volumes of different brain regions, the thickness of the cortex, and the total brain surface area.
These various measurements highlighted highly variable aging between brain regions. However, the rate of degradation was similar between the sexes for most measurements, meaning that the majority of the brain ages in the same way, regardless of sex. Nevertheless, some measurements showed differentiated degradation based on sex. For some, women's brains appeared to age more rapidly: this was particularly true for the volume of the frontal lobe, important for decision-making and reasoning. But while men's brains fared better for this measurement, they exhibited faster aging for a greater number of points. For example, the total brain volume decreased more rapidly in men, and more specifically, the entire gray matter (the cortex) shrank more quickly. This male decline affected approximately 20 of the 87 measurements taken, emphasizing that, overall, men's brains age faster than women's.
Women's brains could be better protected
To confirm their results, the researchers conducted more specific analyses, taking into account factors such as educational level, women's longer life expectancy, or comparing only those over 60. These tests mitigated some of the differences, but the conclusion remained the same: women's brains age better than men's. This result is consistent with previous studies that also showed that women's aging, including brain aging, appears to be slower than men's, perhaps thanks to a female superpower:silent X chromosome awakening.
As a reminder, women have two X chromosomes (XX) compared to only one for men (XY). This means that, in women, the genes on this chromosome are duplicated. Normally, this has no consequence, since one of the copies is systematically silenced. Therefore, only one copy of each pair of genes can be read, thus producing the same quantity of protein as in men. But with age, this silencing system becomes less efficient, and both copies are now readable, therefore generating twice the amount of protein. This is the case, in particular, for a protein that protects neurons, which allows for better preservation of cognitive functions in older women than in their male counterparts.
The mystery remains
So why are women more at risk of developing Alzheimer's disease? The mystery remains, but some clues exist. Even though, in healthy individuals, age seems to be a more significant factor in men's brains, One could imagine that these differences in brain atrophy might differ between healthy and diseased brains.The authors suggest that, in other words, the disease may progress more rapidly in women than in men. Among healthy individuals without risk factors for the disease, women fare better than men, but this could be reversed if only individuals with an increased risk (for example, the APOE4 gene) are considered.
Another possibility could be menopause. It has been shown that certain hormones, such as estrogen, have a protective effect on the brain. And that the drop in their production during menopause could make women's brains more at risk, particularly in those with early menopause. But whatever the reason for this paradox, it is certain that the probability of developing Alzheimer's disease can be reduced, even when these risk factors are present. Physical activity, diet, social connections… The prevention is essential, whether you are a man or a woman.
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