Almost two-thirds of those with Alzheimer’s disease in the United States are women. 1
The first obvious reason for this is that women live longer, but longevity alone does not explain the large difference.
“Even after correcting for age, women appear to be at greater risk,” said Michael Greicius, MD, assistant professor of neurology and neurological sciences and medical director of the Stanford Center for Memory Disorders told Stanford News.
Greicius is the senior author of a 2014 study that analyzed records of 8,000 people, most of whom were over the age of 60.
The study looked at 2588 people with mild cognitive impairment and 5496 healthy elderly who had visited national Alzheimer’s centers between the years of 2005 and 2013.
The researchers examined what type of APOE genes the men and women had and compared them to their cognitive levels.
There are three APOE variants: APOE2, APOE3 andAPOE4. Most people carry two copies of the APOE3 gene variant (one from each parent).
However, about one in five people carry at least one copy of APOE4. That is the gene that has been found to have a link to Alzheimer’s disease, particularly if the person is female.
A study from 1997 had shown “that females with the APOE4 variant were four times more likely to have Alzheimer’s compared with people with the more common, neutral form of the gene. However, in men, APOE4 seemed virtually harmless,” reported AAAS.ORG.
In this new 2014 study, Greicius and fellow researchers found that “healthy women who inherited the APOE4 variant were twice as likely as non-carriers to develop mild cognitive impairment or Alzheimer’s disease, whereas APOE4 males fared only slightly worse than those without the gene variant,” according to AAAS.ORG.
Greicius stated that knowing the difference between the affect of the APOE4 gene in female and male patients could alert health care providers to take different approaches in the management of Alzheimer’s.
Gene differences are not the only thing being studied to determine why women have developed Alzheimer’s more often than men. Hormones appear to also play a role.
In 2012, a study published in the journal of Neurology found that hormone replacement therapy, when started within five years of menopause, especially if it was used for 10 years or more, may cut the risk of developing Alzheimer's disease by 30 percent in women.
However the researchers also found that women who had started a combined therapy of estrogen and progestin when they were older than 65 years old had a higher risk of dementia.
A previous larger study from 2007 showed similar results according to ABC news. “Women who reported using any form of estrogen hormone therapy before they turned 65 were nearly 50 percent less likely to develop Alzheimer's disease or another dementia than women who did not use such therapy by that age."
"But women who started estrogen-only therapy after the age of 65 had about a 50 percent increased risk of developing dementia. The risk was nearly double among women using combined (estrogen plus progestin) therapy.”
It is too early to determine whether women should or should not start hormone replacement therapy to avoid Alzheimer’s since hormone therapy has been found to contribute to other health problems such as breast cancer, heart attack and stroke.
As more research is gathered, the role and timing of hormone use may be used to make recommendations.
Similarly, knowing the presence of an APOE4 gene may offer guidance in drug development to treat Alzheimer’s. Its role is currently being looked at as part of clinical trials.
This knowledge may allow medications to focus on the treating or preventing the disease in women versus men.
Sources:
1) Alzheimer's Facts and Figures. Alz.org. Retrieved November 16, 2014.
http://www.alz.org/alzheimers_disease_facts_and_figures.asp
2) Finding May Explain Why Women More Likely Develop Alzheimer's. Science AAAS.org. 14 April 2014. Retrieved November 16, 2014.
http://news.sciencemag.org/biology/2014/04/finding-may-explain-why-women...
3) Gene variant puts women at higher risk of Alzheimer's than it does men, study finds. Stanford Medicine News Center. Apr. 14, 2014. Retrieved November 16, 2014.
http://med.stanford.edu/news/all-news/2014/04/gene-variant-puts-women-at...
4) Starting Hormone Therapy Within 5 Years After Menopause Cuts Alzheimer's Disease Risk by Nearly a Third. Medical Daily. Oct 24, 2012. Retrieved November 16, 2014.
http://www.medicaldaily.com/starting-hormone-therapy-within-5-years-afte...
5) Hormone Therapy May Protect Against Alzheimer's. ABC news. May 23, 2007. Retrieved November 17, 2014.
http://abcnews.go.com/Health/Healthday/story?id=4506803
Study abstracts:
6) Altmann, Andre PhD et al. Sex modifies the APOE-related risk of developing Alzheimer disease. Ann Neurol. 2014 Apr;75(4):563-73. doi: 10.1002/ana.24135. Epub 2014 Apr 14.
http://www.ncbi.nlm.nih.gov/pubmed/24623176
7) Shao, Huibo MS et al. Hormone therapy and Alzheimer disease dementia. Neurology. 2012 Oct 30;79(18):1846-52. doi: 10.1212/WNL.0b013e318271f823. Epub 2012 Oct 24.
http://www.ncbi.nlm.nih.gov/pubmed/23100399
Michele is an R.N. freelance writer with a special interest in woman’s healthcare and quality of care issues. Other articles by Michele are at http://contributor.yahoo.com/user/499625/michele_blacksberg.html
Edited by Jody Smith