Alzheimer’s disease is one of the most common causes of memory loss and cognitive decline in older adults. Yet, one fact has puzzled researchers for years: women make up nearly two-thirds of all Alzheimer’s cases worldwide. It has often been assumed that women’s longer life expectancy explains this difference.
However, new findings suggest that how men’s and women’s brains change with age reveals subtle but meaningful biological differences. These insights could help us understand why Alzheimer’s risk varies by sex and why prevention strategies might need to be tailored differently for men and women.
A recent study published in PNAS examined brain scans from more than 4,700 healthy adults aged between 17 and 95. Researchers wanted to see whether brain ageing patterns differed between men and women and if those differences could help explain why Alzheimer’s is more common among women.
The study analysed over 12,000 brain MRI scans, tracking changes in brain volume, surface area, and thickness over time. The results showed that both men and women experience brain shrinkage as they age, but the patterns are not identical.
Men tended to show greater decline in more brain regions, especially in areas related to memory and emotion, such as the parahippocampal cortex. Women, on the other hand, had fewer areas of decline but showed more noticeable enlargement of brain ventricles, which are fluid-filled spaces. These results indicate that while men may experience faster brain tissue loss with age, women’s brains might be more vulnerable to other forms of change that influence Alzheimer’s development.
Biological ageing affects men and women differently. The research found that men’s brains tend to show signs of faster structural ageing, similar to how men generally exhibit quicker overall biological ageing. Factors such as hormones, metabolic function, and epigenetic changes — which influence gene expression — might play a role.
Interestingly, even though men appear to lose brain tissue faster, women are still more likely to develop Alzheimer’s. This suggests that factors beyond physical brain shrinkage are at work. For instance, the study noted that when differences in life expectancy were taken into account, some of the male-specific patterns of brain ageing disappeared.
This means that longevity may mask or exaggerate certain effects in studies that do not separate lifespan differences. Researchers also pointed out that women’s brains might experience unique hormonal shifts during menopause, affecting how the brain processes energy and clears toxins. These changes could make certain brain regions more susceptible to Alzheimer related damage, even if overall atrophy is slower than in men.
The study highlights that brain ageing and Alzheimer’s risk are not identical processes. In simple terms, a shrinking brain does not automatically mean a higher chance of Alzheimer’s. The researchers found that while men’s brains might decline more rapidly in structure, women’s brains could be more sensitive to the specific biochemical changes linked to the disease.
