Alzheimer’s disease has long shown a troubling gender divide: nearly two-thirds of Americans living with the condition are women. Now, new research offers a fresh lead on why that might be.

A large study published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association has found that women with Alzheimer’s carry distinct imbalances in brain-related fats—lipids—compared to both healthy women and men with the disease. These differences may help explain why women are more vulnerable and open the door to strategies for prevention.

Lipids and the brain’s wiring

Lipids are more than just fats stored in the body. In the brain, they form the building blocks of cell membranes, help transmit electrical signals, and protect nerve fibers. Some, like omega-3 fatty acids found in salmon and flaxseed, are anti-inflammatory and supportive of brain health. Others—saturated and trans fats—are linked to cellular damage and disease.

To better understand how lipids factor into Alzheimer’s, researchers in the UK analyzed blood samples from 841 people: 306 with Alzheimer’s disease, 165 with mild cognitive impairment, and 370 without memory problems. The group included both men and women, but none with other neurological disorders.

Using a detailed technique called lipidomics, scientists measured hundreds of fat molecules, focusing on 268 that passed rigorous quality checks. Their aim: to see whether lipid profiles varied by sex in ways that could illuminate Alzheimer’s biology.

A clear pattern in women, not men

The results were striking. Women with Alzheimer’s had far lower levels of beneficial omega-3–rich lipids, including DHA and EPA, and higher levels of unhealthy fats compared with healthy women. These disruptions were strongly tied to poorer cognitive test scores.

In contrast, men with Alzheimer’s showed no meaningful lipid differences compared to men without the disease. Out of 268 lipid types studied, 32 were significantly altered in women, while none were linked in men.

The findings suggest that Alzheimer’s progression may be closely tied to the way women’s bodies handle fats. Researchers point to possible disruptions in enzymes that normally process healthy fats, and to reductions in a group of protective fats called plasmalogens—molecules that guard against inflammation and cell damage.

Why women may be more vulnerable

Experts say the results underscore the importance of studying men and women separately when it comes to Alzheimer’s research.

“All too often, data from both sexes are lumped together,” said Dr. Allison B. Reiss, a professor at NYU Grossman Long Island School of Medicine who was not involved in the study. “This research makes clear that metabolism, hormones, and disease risk don’t work the same way in women and men.”

Part of the explanation may lie in biology unique to women. Women process polyunsaturated fats more rapidly, in part because omega-3s are critical for fetal brain development during pregnancy. That efficiency, while beneficial early in life, could leave women more prone to depletion later on, said Dr. Timothy Ciesielski, a population health researcher at Case Western Reserve.

Can omega-3s help?

The findings add weight to the idea that boosting omega-3 intake might benefit women at risk for Alzheimer’s, though experts caution it’s far from proven.

“Healthy diets that include omega-3s are important, but no single nutrient is a magic bullet,” Reiss said. “Eating a wide variety of fruits, vegetables, and whole foods will do far more than trying to overload on one compound.”

Still, the study adds a crucial piece to the Alzheimer’s puzzle: fats may not affect everyone the same way, and women in particular could gain from targeted nutritional and medical strategies.

As Alzheimer’s cases in the U.S. climb past 7 million—and are projected to nearly double by 2050—such insights may help chart a clearer course toward prevention and care.