Over 7 million people in the United States are living with Alzheimer’s disease. Unfortunately, this number is expected to double by 2050. Women outnumber their male counterparts by almost a two-to-one margin. Although in general, women tend to live longer than men, aging alone cannot account for the differences in the number of women who are disproportionately represented. What factors account for the sex difference?

Women have two X chromosomes, whereas men have one X and one Y chromosome. Just because women have two X chromosomes does not mean they have twice as much genetic material, because one of the female X chromosomes is silent. In addition, the APOE gene, which is the strongest genetic risk factor for late-onset Alzheimer’s, is more pronounced in females.

Genes on the X chromosome are related to immune function, brain function, and Alzheimer’s disease. Inflammation has been linked to many chronic diseases, including neurodegenerative ones like Parkinson’s and multiple sclerosis. Research published by UCLA Health describes a sex-linked gene that promotes inflammation in the brain. In their animal studies, the researchers identified a gene on the X chromosome linked to the production of inflammatory proteins in the brains of experimental animals. When the researchers deactivated the responsible gene, the neurodegenerative pathology in the animals was ameliorated. They propose that, since women carry two X chromosomes, this may help explain sex-related differences in diagnosis.

Estrogen may act as a protective agent against neurodegeneration. As women age, levels of estrogen decline, and exposure to cellular toxicity and the accumulation of amyloid proteins increases. Both phenomena may play a role in the increased incidence of AD in females. A report in The International Journal of Geriatric

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