Two-thirds of U.S. Alzheimer’s cases are women, and it’s not just because they live longer. New research offers some biological clues as to why women might be more likely than men to develop Alzheimer’s disease (AD) and how the most common form of dementia varies by sex.  There is now evidence that the disease might spread differently in the brains of women than in men. Previous studies suggested that women at any age are more likely than men to develop AD. Scientists also know that compared with men, the APOE-4 gene appears to increase the risk more for women in certain age groups.

However, women who have early-stage AD could go undiagnosed as they generally do better on verbal tests than men, which could mask any Alzheimer’s damage. Analyzing scans from more than 1,000 older adults, University of California, San Diego researchers found that women’s brains were better at metabolizing sugar. This might compensate for any damage caused by dementia, making it less likely that they would be diagnosed by tests that involve verbal skills.

Vanderbilt University researchers discovered differences in how the tau protein spreads in the brains of women compared to men. They found that tau networks in women with mild impairment were more diffuse and spread out than in men, suggesting that more areas of the brain were affected. Work and family experience also seem to affect women’s risk of memory problems in later life. After the age of 60, women who had previously been working had a slower memory decline than women who had not been engaged in paid work. The benefit held regardless of whether the women were married or had children, or whether they had temporarily left the workforce for family reasons.

Although the study did not attempt to show why working made a difference, possibilities include cognitive stimulation, and social and financial benefits of working. As poverty contributes to mental decline in later life, financial independence could be important.  Until recently, many researchers believed that more women were living with Alzheimer’s because they typically live longer than men. However, the latest research suggests that being female is an important factor in and of itself.