Men’s brains shrink faster with age than women’s, study finds

Men’s brains appear to shrink faster than women’s as they age - yet Alzheimer’s disease continues to affect women far more often, according to new research.

According to the World Health Organization (WHO), 57 million people had dementia worldwide in 2021, and every year, there are nearly 10 million new cases.

But there is a striking gender difference. Globally, Alzheimer's disease (AD) is nearly twice as prevalent in women compared to men. At age 45, a woman’s lifetime risk of developing the disease is one in five, compared with one in ten for men.

For years, scientists have been left puzzled over this disparity, questioning whether differences in how men’s and women’s brains age might hold the answer.

But a new study published in Proceedings of the National Academy of Sciences suggests that this may not be the case.

What the research found

Analysing more than 12,000 brain scans from nearly 5,000 healthy people aged between 17 and 95, researchers found that men’s brains show a steeper decline in several regions over time, including areas involved in memory, movement and visual processing.

For example, the postcentral cortex, the part of the human brain that processes sensations such as touch, pain and body position, shrank 2.0 per cent per year in men - nearly twice the 1.2 per cent annual decline in women.

Women, on the other hand, showed more pronounced expansion of the brain’s fluid-filled ventricles, a sign of age-related change, but less extensive structural loss overall.

Additionally, men showed greater age-related thinning of the cortex – the brain’s outer layer – particularly in regions such as the parahippocampal and fusiform areas.

They also experienced a sharper decline in subcortical structures such as the putamen and caudate, which play key roles in motor function.

Why are women more likely to develop Alzheimer’s despite slower brain shrinkage?

The results of the study suggest that sex differences in age-related brain decline are unlikely to contribute to the higher Alzheimer’s disease diagnosis prevalence in women.

Scientists have long pointed to a complex mix of factors: hormonal changes after menopause, differences in immune and vascular function, genetic risk factors such as the APOE ε4 gene, and the simple fact that women tend to live longer than men.

In 2021, the average life expectancy was 73.8 years for women versus 68.4 years for men. Thus, more women reach ages when Alzheimer’s risk is highest. The disease is most common in people over the age of 65, according to the UK's National Health Service.

The biological reasons women remain more vulnerable are still poorly understood – but it is increasingly clear that the answer will not be found in structural brain scans alone.