Women are twice as likely as men to develop Alzheimer’s disease — but scientists are still trying to understand why.

One key reason: Women were historically excluded from medical research. It wasn’t until 1993 that U.S. lawmakers required federally funded studies to include women. Researchers have been working to close that knowledge gap ever since.

Now, new research is helping scientists better understand why women’s brains may be more vulnerable to Alzheimer’s — and what might help lower the risk.

Alzheimer’s tau tangles build up faster in women

In Alzheimer’s disease, toxic proteins called beta-amyloid and tau form in the brain, disrupting normal function. But could these proteins build up faster in women?

A new study in JAMA Neurology tracked tau levels in 1,376 healthy older adults over three years, focusing on those with high beta-amyloid levels — a known Alzheimer’s risk factor. The results showed that women at risk developed tau tangles faster than men.

Since tau buildup is linked to cognitive decline, this may help explain why women are more likely to develop Alzheimer’s.

Early menopause could speed up the disease

Estrogen, a hormone that supports brain health, may play a key role in Alzheimer’s risk. Could an early drop in estrogen — such as through early menopause — trigger damaging changes in the brain?

A study of 268 women in the Rush Memory and Aging Project found that those who experienced menopause before age 50 had more tau tangles and worse synaptic integrity — a measure of how well brain cells connect and communicate. The findings highlighted the importance of hormone replacement therapy after menopause and added to evidence that estrogen may protect the brain.

Blood vessels in women’s brains age differently

The blood vessels that supply the brain with oxygen and nutrients age over time, a process known as angiogenesis. More new research suggests this process may affect women’s brains differently.

A recent study in Science Translational Medicine measured angiogenesis biomarkers in healthy adults and found that higher levels were linked to better cognitive performance in younger women — but worse performance in older women. This pattern wasn’t seen in men.

Understanding why women are more vulnerable to Alzheimer’s is a crucial step toward catching the disease early and developing targeted treatments.