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Thursday, May 15, 2014

By the Numbers: Why Women with Alzheimer’s Outnumber Men with the Disease

By Gina Shaw

At first, the fact that almost two-thirds of Americans with Alzheimer’s disease are women would seem to have a simple explanation: women live longer than men (81 vs. 76 years average life expectancy in the US), and Alzheimer’s disease risk increases greatly with age.

But a new special report on women and Alzheimer’s disease, released by the Alzheimer’s Association as part of their larger annual report, 2014 Alzheimer’s Disease Facts and Figures, makes it clear that the significant gender gap in Alzheimer’s almost certainly cannot be explained by life expectancy alone.

As the report notes, women aged 65 have a one in six lifetime risk of developing Alzheimer’s, while men aged 65 have a one in 11 risk — a difference that can’t be accounted for simply by five years increased average lifespan.
To some extent, gender differences in Alzheimer’s rates may be explained by similar differences in cardiovascular disease rates. A recent analysis of data from the Framingham study — published in January in the Alzheimer’s Association journal, Alzheimer’s & Dementia — confirmed that men aged 45-65 have a higher rate of death from cardiovascular disease than women of the same age range. Since a high risk of cardiovascular disease is also associated with a high risk of developing Alzheimer’s disease, these early heart disease deaths among men means that a significant number of men who might otherwise have gone on to develop Alzheimer’s have died of heart disease before reaching age 65.

But again, the researchers on this analysis found that this effect explained only part of the difference in Alzheimer’s disease rates among women and men 65 and older — perhaps 20 to 50 percent. 

      So what else is at play here? It’s possible that these differences can all be explained by research methodology. “Several European studies showed higher incidence rates in women; however, studies in the United States did not show the difference,” Walter A. Rocca, MD, MPH, director of the Rochester Epidemiology Project at the Mayo Clinic, told Neurology Today. “The different pattern in Europe and the United States may be due to differences in the methodology used to conduct the study. On the other hand, the differences may be genuine, and may reflect a different distribution of risk and protective factors related to sex or gender across countries (or continents).”

      See the full discussion by Alzheimer’s experts
here in the May 1 issue of Neurology Today. Browse our archives for recent research advances in Alzheimer’s and dementia: