Study details and key findings

For the study, researchers used mass spectrometry to analyze plasma samples from 841 participants who were part of the AddNeuroMed biomarker cohort in Europe and the Dementia Case Register cohort in England. Of the participants, 306 had Alzheimer's disease, 165 had mild cognitive impairment, and 370 were cognitively healthy.

Among the participants with Alzheimer's, the mean age at diagnosis was 73, and the mean duration of the disease was 3.74 years. On average, participants with Alzheimer's were older than those with cognitive impairment or controls.

The researchers identified 268 single lipids for each sample and investigated whether there were sex-specific associations of lipid modules and single lipids with Alzheimer's disease. Overall, three lipid modules in women and one in men were associated with Alzheimer's disease.

In women, a total of 37 lipids were significantly associated with Alzheimer's disease compared with controls. Women with Alzheimer's had higher levels of saturated lipids and up to 20% lower levels of unsaturated lipids, including omega fatty acids.  

Commentary

Fats play important roles in maintaining a healthy brain, and according to the researchers, the study's findings could help scientists understand why more women are diagnosed with Alzheimer's disease than men.

The study reveals that Alzheimer's lipid biology is different between the sexes, opening new avenues for research, Legido-Quigley said. "Our study suggests that women should make sure they are getting omega fatty acids in their diet through fatty fish or via supplements."

Diets that are high in omega-3 fatty acids, such as the Mediterranean diet, have been long associated with positive health benefits, including for the brain. For example, a 2022 study found that middle-aged people with higher levels of omega-3 fatty acids in the blood had better cognitive function compared to others.

However, evidence about the effect of omega-3 supplementation on cognitive outcomes has been inconsistent. So far, several clinical trials testing omega-3 supplements in older adults have not found any improvements to cognitive function or increase in mental capacity in people already diagnosed with dementia.

In the future, Legido-Quigley said she wants to see a clinical trial to test whether supplements can delay Alzheimer's disease specifically in women with low levels of unsaturated fatty acids, noting that this decline may start when women are in their 50s.

According to Julia Dudley, head of research at Alzheimer's Research UK, which cofunded the study, more research is needed to fully understand the mechanism behind the difference and to find out if lifestyle changes, including diet, could have an impact on the disease.

"Understanding how the disease works differently in women could help doctors tailor future treatments and health advice," Dudley said.