Men experience faster brain shrinkage as they age than women, yet Alzheimer’s disease remains nearly twice as common in women, according to a new study that challenges long-held assumptions about the roots of the gender gap in dementia.
The research, published this week in the Proceedings of the National Academy of Sciences (PNAS), examined more than 12,000 brain scans from nearly 5,000 healthy individuals aged 17 to 95. The findings show that while men’s brains show a steeper rate of decline across several key regions, this does not explain why women are far more likely to develop Alzheimer’s disease.
According to the World Health Organization (WHO), around 57 million people were living with dementia in 2021, with nearly 10 million new cases recorded annually. Alzheimer’s disease — the most common form of dementia — disproportionately affects women, with one in five developing the disease by age 45, compared to one in ten men.
For decades, scientists have sought to determine whether structural differences in how male and female brains age could explain this disparity. However, the new study suggests otherwise.
Researchers found that men’s brains tend to shrink faster in multiple regions linked to memory, sensory processing, and movement. The postcentral cortex — the part of the brain that processes sensations such as touch and pain — declined by 2% per year in men, compared to 1.2% in women. Men also exhibited greater thinning in the cerebral cortex, particularly in regions tied to memory and visual recognition, such as the parahippocampal and fusiform areas.
Additionally, men showed more pronounced decline in subcortical structures including the putamen and caudate, which are critical for movement control. Women, by contrast, showed more fluid accumulation in the brain’s ventricles — a sign of normal ageing — but retained more structural integrity overall.
Despite this, women continue to face a far higher risk of Alzheimer’s disease. Experts say the reasons lie beyond structural brain changes, pointing instead to hormonal, genetic, and lifespan factors.
“Hormonal changes after menopause, vascular and immune differences, and genes like APOE ε4 all play a role,” said one of the study’s authors. “Women also live longer than men, which naturally increases their risk.”
Globally, women’s life expectancy is about five years longer than men’s — 73.8 years versus 68.4 years in 2021 — meaning more women live into the age range where Alzheimer’s risk is highest.
The findings underscore the complexity of Alzheimer’s and the need to explore biological and environmental factors beyond simple brain volume loss. As the researchers concluded, the key to understanding women’s greater vulnerability to dementia “will not be found in brain scans alone.”
