Alzheimer’s disease affects millions of people around the world, but women are far more likely than men to be diagnosed with the condition.
Many experts have assumed this is mostly because women live longer than men, and Alzheimer’s tends to strike later in life. However, a new study suggests that the story may be more complex—and possibly surprising.
The study, published in the journal Proceedings of the National Academy of Sciences, looked at brain scans from over 4,700 healthy people between the ages of 17 and 95. Each person had at least two brain scans, with a total of more than 12,600 brain MRIs analyzed.
The goal was to understand how men’s and women’s brains change as they age, and whether those changes could help explain the higher Alzheimer’s rates in women.
Researchers found that men’s brains actually showed more signs of decline over time than women’s brains. In men, there was a bigger reduction in both cortical thickness and surface area in many areas of the brain.
These parts of the brain are important for memory, thinking, and processing information. Men also showed more decline in deep brain structures as they aged. Women, in contrast, had fewer regions where the brain shrank but did show more expansion of the brain’s fluid-filled spaces (called ventricles), especially later in life.
These results challenge the idea that women are more prone to Alzheimer’s just because their brains decline faster. Instead, they suggest that the answer lies elsewhere. The authors of the study point out that other factors might be driving the higher Alzheimer’s rates in women.
One possibility is genetics. A specific gene variant called APOE ε4 is linked to a higher risk of Alzheimer’s. Some studies suggest that this gene may work differently in men and women, affecting how proteins build up in the brain.
Hormonal changes, especially after menopause, could also play a role in how the brain ages. Social and cultural factors—such as how women and men seek medical care or are diagnosed—might also contribute.
There’s also the issue of lifespan. Since women live longer on average, they have more time to develop Alzheimer’s. The researchers tried to adjust for this in their analysis.
When they did, some of the brain aging differences between men and women became less clear, and new ones appeared. For example, they found that after adjusting for life expectancy, women showed more shrinkage in the hippocampus, a part of the brain crucial for memory.
Another complication is that the people in this study were mostly well-educated, and education is known to protect against Alzheimer’s. This means the sample might not fully represent the general population, especially men who may be less healthy or less educated.
The authors say that while their study offers valuable insights, it also raises new questions. It’s still unclear whether the brain changes they found are caused by aging itself or by how close a person is to death, which can also affect the brain. And because of differences in who was included in the study, the results should be interpreted carefully.
Even so, this research is an important step forward. By carefully studying how the brain changes over time in both men and women, scientists are getting closer to understanding why Alzheimer’s affects people differently. The answers could help shape better prevention and treatment options for everyone in the future.
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The study is published in PNAS.
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