It’s been known by the scientific community for a long time that women resist the symptoms of Alzheimer’s better than men. It was a groundbreaking discovery that opened a lot of doors for the research of the disease. At first, it wasn’t clear why this happened. However, recent advances in research have pointed to female chromosomes as the reason.
An August of 2020 report from researchers at the University of California San Francisco reveals that females might have a greater resistance to Alzheimer’s Disease–and generally live longer once they receive a diagnosis. This study concludes that this resistance stems from having an extra “X” chromosome.
In this article, you’ll learn what studies have revealed about female chromosome resistance to the disease and why they resist more than male chromosomes. First, you should know some basics about the disease to understand the information provided by the studies. Keep reading to find out more.
The Basics of Alzheimer’s Disease
This disease is a degenerative brain disease that causes severe memory loss and other cognitive functioning problems. It’s a form of dementia. Many people use the term with dementia interchangeably, but dementia is a term that describes the symptoms of a group of diseases. Think of dementia as the make and Alzheimer’s as the model.
Stages of the Disease
The disease can generally be separated into three stages:
- Early-stage (mild) – the person may still lead an everyday life but may forget the location of objects, have trouble coming up with familiar words, have trouble with planning, or other simple memory-related problems.
- Middle-stage (moderate) – the person may get words mixed up, have severe mood swings, display bizarre behavior like not wanting to bathe, have trouble with incontinence, and essentially need a greater level of care make it from day to day.
- Late-stage(severe) – they will require around the clock care. The person has difficulty communicating, physical abilities may diminish, and they may be vulnerable to infections.
On average, women seem to resist the changes longer in the early and middle stages. Although the rate of progression in late stages speeds up for women, they still live longer than men because of the slow decline in the first two stages.
Statistics on Alzheimer’s
*These statistics are provided by the Centers for Disease Control (CDC) and the World Health Organization (WHO).
- Around 50 million people worldwide suffer from dementia-related diseases.
- Alzheimer’s is the most common form of dementia and makes up about 70% of cases.
- By 2060, 14 million people are expected to suffer from the disease.
- Symptoms appear after the age of 60 and get worse with age.
- The disease is one of the top ten leading causes of death in the United States.
- It is also the fifth leading cause of death for seniors ages 65 and older.
What Causes Alzheimer’s
Unfortunately, scientists have not yet discovered what causes the disease. There are several proposed risk factors, but scientists know for sure that age is a factor. As of now, it’s the primary factor. However, the disease is not a normal part of aging.
Genetics is another proposed risk factor as well as education, diet, and environment. There is a lot of speculation about risk factors and causes, but unfortunately, scientists don’t know a lot about the disease yet. However, as research has progressed, a few interesting findings have come about. One of them is the fact that female chromosomes resist the disease more than male chromosomes.
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Why Female Chromosomes Resists the Disease More Than Male Chromosomes
According to Dena Dubal, MD, Ph.D., associate professor of neurology at UCSF, more women than men develop the disease since women live longer. This longevity puts them more at risk since age is a primary factor in developing the disease.
However, women are much more resistant to the symptoms than men are, so they live longer with the disease. Research also shows that women remain in the first and second stages longer than men do, supporting the research that shows they live longer. While this seems to be great news for women, keep in mind that, genetically-speaking, this also means that you’re more likely to develop the disease from your mother rather than your father.
For a long time, it was unclear why this gender anomaly was true. Recent breakthroughs in the research revealed that female chromosomes held the answer.
The X Chromosome
Most people are familiar with male and female chromosomes, but here is a quick breakdown for people who may not be up to date on the science. Prepare yourself for a short science lesson.
At the time of fertilization, an embryo receives a chromosome from each parent. This chromosome determines the gender of the future child. If it’s a girl, she will get an X chromosome from each parent. If it’s a boy, he will get an X chromosome from the mother and a Y chromosome from the father.
When you put all that together, you get:
- Women have two X chromosomes.
- Men have an X chromosome and a Y chromosome.
Some people say that because of this configuration, men determine the gender of the child. However, that’s another discussion for another article. This discussion will detail the significance of this as it relates to Alzheimer’s disease.
People often refer to the X chromosome as the female chromosome, although this is technically incorrect – as you can see, both men and women have an X chromosome. However, it’s referred to as such because if the embryo gets an X chromosome from the father, it will be a girl. Throughout the article, the X chromosome will continue to be referred to as the female chromosome for simplicity.
The KDM6A Gene
The X chromosome is the reason that women tend to resist the disease more than men. It’s because women have two X chromosomes and these chromosomes have genetic protection against the disease. In other words, women naturally have twice the protection that men have.
There is a gene in the X chromosome called KDM6A that produces a protein to protect against the disease. There are two “strengths” of KDM6A. Think of one as regular strength and the other as extra strength.
Research shows that 13 percent of women worldwide are lucky enough to have two different strengths, KDM6A genes, giving them even more protection. Seven percent of men have one extra strength, the KDM6A gene, but they still won’t have as much protection as women.
While there is still a lot more research to be done on this particular gene, and scientist don’t think that KDM6A is the key to stopping the disease in its tracks, it is an interesting development. It proves that research into the disease is going in the right direction.
Another Gene that Influences the Risk of Alzheimer’s Disease
There is another gene that is being researched as it relates to the disease. Scientists discovered a Colombian woman that proved to be a groundbreaking subject for a case study into the APOE gene, which is contained in chromosome 19.
If you aren’t sure about this, you get two of chromosome 19 – one from your mother and one from your father.
APOE is a gene that comes in three variants: APOE2 lowers the risk of the disease, APOE3 doesn’t have any effect; APOE4 increases the risk. Around half of people with Alzheimer’s have APOE4, although APOE4 only affects about 20% of the population. That means that 80% of the population has one of the other two versions. From this statistic, you can deduce that fewer women have the risky APOE4 version than men, which is a minor factor that could play into why they’re more resistant to the disease.
APOE4 seems to encourage the formation of sticky plaques of the protein beta-amyloid. This protein clogs the brain in people with the disease. However, scientists do not believe this is a cause of the disease, but rather a symptom.
Referring back to the Columbian woman in the case study, she had APOE3. Due to a genetic mutation that ran in her family, causing a disproportionate number of them to develop the disease in their early 40’s, she had that genetic mutation also. However, scientists were baffled because she didn’t start showing symptoms until after 70 years old.
Scientists discovered that the woman had plenty of beta-amyloid. However, she barely had any of the protein Tau, which is a hallmark protein of people suffering from the disease. This is what led researchers to look into the different versions of APOE more closely.
Final Thoughts on the Female Chromosome Resistance to Alzheimer’s Disease
There is a lot more research to be done on this mentally debilitating disease. There are a lot of theories, but only a small amount of facts that researchers are trying to sort and link together. However, discoveries like that of the Columbian woman help lead to new breakthroughs.
It’s a fact that women are more resistant to the disease than men. Knowing about female chromosomes being more resistant to the disease than men’s is a groundbreaking discovery that will eventually open a lot of doors in the research. As it becomes more and more clear which genes play a role in this ravaging disease, the scientific community will get closer to a treatment and even an eventual cure.
