Scientists continue to study how our brains change with age. Recently, a longitudinal study in the Proceedings of the National Academy of Sciences suggests that when considering the volume of the brain, men’s brains shrink at a faster rate than women’s.

This raises the question: if the male brain declines faster, how is it that women are more likely to develop Alzheimer’s disease?

The brain’s aging involves a natural, gradual loss of volume, but this doesn’t happen evenly.

A large study analyzing 12,638 brain scans from over 4,726 cognitively healthy participants found that the male brain showed a greater overall reduction in volume across many regions compared to the female brain.

This study examined brain changes using MRI scans.

Scientists compared multiple scans taken from the same individuals over several years to accurately track the thickness of different regions as they develop.

Men especially exhibited a much greater loss of gray matter and faster thinning of the brain’s cortex in key areas.

For example, the prefrontal cortex, the area in charge of complicated tasks and decision making, shrank by about 2% per year in men, versus 1.2% in women.

Men also experienced greater ventricular expansion, which is the fluid-filled spaces in the brain, as a result of tissue loss.

On the other hand, women lose tissue at a slightly slower rate.

However, the hippocampus, the brain’s main memory center, showed no significant difference in volume loss between males and females.

The researchers suggest that the observed difference in healthy aging may not fully explain why women face a higher risk of Alzheimer’s. However, one major factor is longevity: women generally live longer than men, which allows for more time for the disease to develop.

Another cause could be biological changes related to menopause, which involves significant hormonal shifts that might affect the brain’s health beyond simple volume measurements.

By understanding the “normal” aging timeline for both sexes, scientists can better identify when those changes signal the start of a neurodegenerative condition.

The first step toward future prevention or delay of diseases such as dementia is to identify the point at which brain changes signal a problem, as this study aims to do.