Women are more likely than men to get Alzheimer’s, but their lifespan post disease is also longer. Men also show more cognitive deficits than women. This means that while women may be more likely to contract the disease, its progression is less aggressive. Recent research may have finally cracked the reason behind women’s resilience to Alzheimer’s. A review of animal and human studies by scientists at UC California revealed that sex chromosomes in women offer them double protection against the ravages of the disease.
Published in Science Translational Medicine, the findings show that some people have an especially potent variant on the chromosome. Animal studies with mouse models revealed the x chromosome affected Alzheimer’s-related vulnerability. When the mice were engineered to carry a second X chromosome, the team noticed marked resilience. This was in part due to an X chromosome gene known as Kdm6a. The human variant of this gene is associated with slower cognitive decline and higher expression. 
An especially active variant of Kdm6a is present in 7 percent men and 13 percent women. Since women have two X chromosomes, their chances of carrying this gene also increase. Some women have two copies of the gene. Long-term studies with elderly people, some of whom had mild cognitive impairment, revealed that women with the gene showed a slower progression towards Alzheimer’s. The data on men was inconclusive because of lack of any significant numbers.
The studies reveal that women carry more of the Kdm6a protein than men. It also revealed that Kdm6a protein is in a higher number in areas in the brain that get first get affected due to Alzheimer’s. This led the team to theorize that the brain produces the protein to fight against Alzheimer’s.