Research studies are continuously trying to explain why more women are affected by Alzheimer's disease than men. There are various biological and genetic factors that cause this discrepancy. The average life expectancy for women is 81 years, for instance, compared to 76 years for men which makes woman more susceptible to dementia, including Alzheimer’s.
However, researchers are attempting to understand the underlying reasons as to why women are more affected by the disease. Researchers are also working on the development of gender-specific treatments.
According to the 2015 Alzheimer's Disease Facts and Figures from the Alzheimer’s Association, out of the 5.1 million people age 65 and older with AD living in the United States, 3.2 million are women and 1.9 million are men.
A large part of the research done on this topic points to two factors: genetics and hormones. A gene known as APOe4 is found in 20 percent of the population. Men and women have about the same chances of carrying the APOe4 gene, which produces a protein in the liver that transports cholesterol and fatty acids in the body. The risk is 10 times higher for someone who has two copies of the gene.
According to an article in the Washington Post, research suggests that the APOe4 gene confers its Alzheimer’s risk unevenly in women. A study led by Michael Greicius, medical director of Stanford Center for Memory Disorders, found that women with the APOe4 gene were twice as likely to get Alzheimer’s as women who did not carry the gene.
The risk factor appeared to be slightly different between men who had the gene and those who did not.
According to Walter A. Rocca, professor of neurology and epidemiology at the Mayo Clinic in Rochester, Minnesota, women who carry the APOe4 gene have a much higher risk of getting Alzheimer’s than men of the same age who do not have the gene.
While this phenomenon is not fully understood, scientists think that the APOe4 gene appears to interact with estrogen to create certain conditions that can lead to Alzheimer’s.
The role of estrogen in relation to Alzheimer’s is a topic that is continuously researched. Estrogen is a steroidal hormone, produced in a woman’s ovaries and adrenal glands, and is known for its critical role in the development of female sex characteristics and reproduction.
Estrogen also acts as a signaling molecule in genes, cells and organs. It is a regulator of metabolism in the female brain, as well.
A postmenopausal women’s estrogen level drops, which causes a series of effects. One of these effects is a decline in the brain’s ability to burn glucose for energy. Without glucose, the brain turns to burning ketone bodies as a source of energy. Ketone bodies are compounds produced from carbohydrates and fat in the liver.
Ketone bodies are not as efficient as glucose in producing energy. As a result, it creates byproducts that damage brain cells. Basically, a postmenopausal decline in estrogen production, and its effects on metabolic activity in the brain, can be linked to higher rates of Alzheimer’s in women.
Suzanne Craft, a professor of gerontology at Wake Forest University’s School of Medicine, researches the way problems with metabolism can damage the brain. In regards to burning ketone bodies instead of glucose to produce energy, Craft explains it is analogous to burning rubber tires instead of propane.
“You’ll get heat, but you’ll get a lot of toxic byproducts as well,” she said in an article at Washingtonpost.com.
Scientists have suspected that estrogen might benefit the brain because of its anti-inflammatory properties. According to the Washington Post, research has found that women whose ovaries are removed are at higher risk for dementia.
A clinical trial run by the Women’s Health Initiative discovered that women ages 65 to 79 who received estrogen-only hormone therapy ran a higher risk of developing dementia, including Alzheimer’s.
The timing of hormone therapy has been found to play a role in reducing the risk of Alzheimer’s. Women who used estrogen replacement within five years of menopause reduced their chances of developing Alzheimer’s. However, women who were given estrogen more than five years after menopause did not share that same benefit.
"Women who used estrogen alone or with progestin late in life increased their risks of dementia, the study found," reported the Washington Post.
In order to understand Alzheimer’s better, and in order to develop gender specific treatment plans, scientists are continuing to study the genetic and hormonal factors that cause women's susceptibility to Alzheimer’s disease.
Source:
A place for mom. How Alzheimer’s impacts men and women differently. November 9 2015.
http://www.aplaceformom.com/blog/3-28-14-alzheimers-impacts-men-women-differently
Alzheimer’s Association. 2015 Alzheimer’s Facts and Figures. November 9 2015.
https://www.alz.org/facts/downloads/facts_figures_2015.pdf
Everyday Health. Alzheimer’s: A woman’s disease? November 9 2015.
http://www.everydayhealth.com/alzheimers/alzheimers-and-gender.aspx
The Washington Post. Why do more women get Alzheimer’s? Research points to genetics, other factors. November 11 2015.
https://www.washingtonpost.com/local/with-women-perhaps-facing-higher-risk-of-alzheimers-female-scientists-unite/2014/09/03/2aa0506c-28ab-11e4-8593-da634b334390_story.html
Reviewed November 12, 2015
by Michele Blacksberg RN
Edited by Jody Smith