New Studies suggest women's brains are more vulnerable to Alzheimer's than men’s.

Two-thirds of all individuals in the US diagnosed with Alzheimer’s are women — a circumstance long explained by scientists by the fact that women live longer than men. 

Two new studies presented at the 2015 Alzheimer's Association International Conference (AAIC) in Washington, DC suggest there may be more to the story.

The studies indicate that women's brains may in fact be more vulnerable to the degenerative effects of Alzheimer's disease than men’s, and that these differences may also cause them to experience memory loss and other declines in cognitive function twice as fast as men.

The first study conducted at Duke University used data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) to study how the cognitive abilities of about 400 seniors (141 women, 257 men) with Mild Cognitive Impairment (MCI) changed over the course of up to eight years.

They found the cognitive abilities of the women declined twice as fast as men's.

“The bottom line is, more and more we think there are some differences,” said Kristine Yaffe, a professor of psychiatry, neurology and epidemiology at the University of California at San Francisco. “It’s not just that women are living to be older — that’s true, and that drives some of this. But there’s something else going on in terms of biology [and] environment for women compared to men that may make them at greater risk or, if they have some symptoms, may change the progression.”

Katherine Amy Lin who reported on the study said, "Our findings suggest that men and women at risk for Alzheimer's may be having two very different experiences."  "Our analyses show that women with mild memory impairments deteriorate at much faster rates than men in both cognitive and functional abilities. These results point to the possibility of as yet undiscovered gender-specific genetic or environmental risk factors that influence the speed of decline. Uncovering those factors should be a high priority for future research."

The second study conducted at University of California at San Francisco used PET (positron emission tomography) scanning to measure levels of amyloid (the substance that forms sticky plaques in the brains of Alzheimer's patients) in about 1,000 people, including many with cognitive impairment or Alzheimer's disease. 

“This study shows women have more amyloid in their brain than men in general, and especially once the women are in the late stages where they’re having dementia,” said Michael W. Weiner, a radiology professor at UC San Francisco and principal investigator of the Alzheimer’s Disease Neuroimaging Initiative.

As to why women have more amyloid in their brain, Weiner says the answer is still unclear—it may be a function of genetics, or caused by hormonal differences (women have estrogen, men have testosterone) or lifestyle differences; diet, exercise, childbearing.

Learn more about this research Here.