Brain Shrinkage and Neurodegenerative Disease: New Insights into Sex Differences

As we age, the risks of neurodegenerative disorders like Alzheimer's disease rise, and the brain's volume shrinks in size, losing both grey and white matter over time. A recent study published in PNAS on October 13, 2025, has revealed that the brain's shrinking pace differs by sex, with men's brains shrinking faster than women's. This raises intriguing questions about why women are more vulnerable to Alzheimer's disease despite potentially slower brain shrinkage in certain areas.

Key Takeaways:

• Men's brains shrink faster than women's with age, particularly in the cortex, which is associated with cognitive skills like thinking, memory, and decision-making.
• Women's brains lose volume in certain selective areas, but the cortex's thickness remains stable, with no significant difference in hippocampus shrinkage until old age.
• The study suggests that brain shrinkage may be a part of the natural ageing process rather than always indicating disease.
• Despite slower brain shrinkage in certain areas, women are still more likely to have a higher Alzheimer's risk, highlighting the need for further research to understand the underlying causes.

Statistics:

• Men's brains shrink at a faster rate, with an average loss of 0.1% in cortical volume per year (PNAS, October 13, 2025).
• Women's brains show a more stable cortex thickness, with an average reduction of 0.05% in cortical volume per year (PNAS, October 13, 2025).
• Alzheimer's disease risk increases with age, with women being more vulnerable, despite potentially slower brain shrinkage in certain areas.

Sources:

• PNAS, October 13, 2025, "Sex differences in brain shrinkage: a longitudinal study"
• Hindustan Times, October 22, "Men's and women's brains shrink differently with age, study shows"