What Causes Multiple Sclerosis? Everyday Health
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And even people with certain predisposing genetic variants may never get MS. In the general population, the risk of developing MS is about 1 in 750 to 1,000. Ariele Greenfield, MD, a neurologist, neuroimmunologist, and researcher at Sutter Health’s Palo Alto Medical Foundation in California, says the strongest genetic risk factors for MS increase a person’s risk by tenfold. In other words, the risk goes from approximately 0.1 percent to 1 percent if you have these risk factors, which is still very low.
If you have an identical twin who has MS, you still only have about a 25 percent of developing the disease. The risk also increases when you have other close relatives (parents, siblings, and children) who have MS, but significantly less than in identical twins. “There’s an increase, but not a guarantee,” of developing MS when a family member has it, Dr. Greenfield says.
But equal numbers of women and men are affected by primary-progressive MS, a less common type — or possibly stage — of MS associated with more disability. Women’s greater susceptibility to MS overall is thought to be associated with hormonal changes, Dr. Mateen says.A number of studies have found that a large proportion of men with MS have low testosterone levels, and a study published in the journal Multiple Sclerosis found an association between low testosterone levels early in the course of MS and more significant declines in cognitive (thinking) function over time.
A meta-analysis published in March 2016 in the journal PeerJ found that smoking appears to raise the risk of MS more in men than in women, and that current smoking is more dangerous than past smoking.
In response to such studies, many doctors have begun recommending vitamin D supplements for people who have MS, particularly for those who are vitamin D deficient.
Mateen says that while these other conditions don’t cause MS, if you have one autoimmune disease, you have a higher risk of getting a second one, and MS is generally considered an autoimmune disease.
RELATED: What Does the Epstein-Barr Virus Have to Do With MS?
While there’s more to be learned about the connection between MS and concussion, the researchers commented that their results emphasized the importance of protecting young people from head injuries.
What Causes Multiple Sclerosis
By Tammy WorthMedically Reviewed by Jason Paul Chua, MD, PhDReviewed: March 5, 2021Medically ReviewedPossible causes include smoking, genetics, family history, gender, and geographic location.Everyday HealthWhen you have multiple sclerosis (MS), your body’s immune system attacks your central nervous system. This causes inflammation that damages the protective myelin sheath that normally covers the nerve fibers in the brain, spinal cord, and optic nerve, as well as the nerve fibers themselves, according to the National Multiple Sclerosis Society (NMSS).But no one knows exactly what triggers the immune system to attack the central nervous system. Most experts believe it occurs when a person with a genetic predisposition to MS is exposed to certain environmental conditions, such as a low vitamin D level, smoking, or the Epstein-Barr virus, notes the NMSS. Since it isn’t known exactly what causes MS, physicians can’t foresee with certainty who will develop the disease, but they do know there are some things that may put you at higher risk.Most Recent in Multiple Sclerosis
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Genetic Differences Are a Contributing Cause
While small differences in genes are known to contribute to the development of MS, determining exactly what role they play is complicated, says Farrah Mateen, MD, PhD, an associate professor of neurology at Harvard Medical School and neurologist at Massachusetts General Hospital in Boston. There are about 200 genes that each play a small role in increasing your risk of developing MS, according to the NMSS.And even people with certain predisposing genetic variants may never get MS. In the general population, the risk of developing MS is about 1 in 750 to 1,000. Ariele Greenfield, MD, a neurologist, neuroimmunologist, and researcher at Sutter Health’s Palo Alto Medical Foundation in California, says the strongest genetic risk factors for MS increase a person’s risk by tenfold. In other words, the risk goes from approximately 0.1 percent to 1 percent if you have these risk factors, which is still very low.
What About Family History
MS isn't an inherited disease, which means families don’t pass it from one generation to the next. However, you can inherit genes that put you at greater risk of developing MS, according to the NMSS.If you have an identical twin who has MS, you still only have about a 25 percent of developing the disease. The risk also increases when you have other close relatives (parents, siblings, and children) who have MS, but significantly less than in identical twins. “There’s an increase, but not a guarantee,” of developing MS when a family member has it, Dr. Greenfield says.
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Gender and the Risk of Developing MS
Women are 2 to 3 times more likely than men to be diagnosed with relapsing-remitting MS, the most common type of MS, according to the NMSS.But equal numbers of women and men are affected by primary-progressive MS, a less common type — or possibly stage — of MS associated with more disability. Women’s greater susceptibility to MS overall is thought to be associated with hormonal changes, Dr. Mateen says.A number of studies have found that a large proportion of men with MS have low testosterone levels, and a study published in the journal Multiple Sclerosis found an association between low testosterone levels early in the course of MS and more significant declines in cognitive (thinking) function over time.
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The damage that MS causes isn’t visible — it occurs in your brain and spinal cord — but it can lead to a wide range of disruptive symptoms. Learn what happens to the brain from MS, and how to protect this crucial organ.FeaturedOther Possible Contributing Causes of MS
There are a number of other factors that are associated with an increased risk for developing multiple sclerosis, although whether any of them are causative is unknown.Smoking
Smokers and people who are exposed to secondhand smoke have an increased risk of developing MS, according to the NMSS.A meta-analysis published in March 2016 in the journal PeerJ found that smoking appears to raise the risk of MS more in men than in women, and that current smoking is more dangerous than past smoking.
Low Levels of Vitamin D
A growing body of evidence, including a study published in October 2017 in the journal Neurology, suggests that vitamin D deficiency may increase a person’s risk of developing multiple sclerosis.In response to such studies, many doctors have begun recommending vitamin D supplements for people who have MS, particularly for those who are vitamin D deficient.
Geographic Location
People who live in more temperate climates — like Europe, southern Canada, and the United States — have a slightly higher risk of MS than those who live closer to the equator, Greenfield says.Researchers have speculated that this higher risk may be related to less sun exposure in these areas during the colder months and consequently lower levels of vitamin D in the body, according to the NMSS. RELATED: Why Your ZIP Code Matters if You Have Multiple SclerosisObesity
Studies have shown that obesity in childhood and adolescence, particularly in girls, increased the risk of developing MS at a later age. Other studies have shown that obesity in early adulthood may also raise your risk of developing MS.Having an Autoimmune Condition
Your risk of developing MS increases slightly if you have other autoimmune disorders such as thyroid disease, pernicious anemia, psoriasis, type 1 diabetes, or inflammatory bowel disease, according to the Mayo Clinic.Mateen says that while these other conditions don’t cause MS, if you have one autoimmune disease, you have a higher risk of getting a second one, and MS is generally considered an autoimmune disease.
Epstein-Barr Virus
Research has suggested that previous infection with the Epstein-Barr virus (EBV, which causes mononucleosis) is linked to a higher risk of developing MS.RELATED: What Does the Epstein-Barr Virus Have to Do With MS?
Concussion in Adolescence
In a study published online in October 2017 in Annals of Neurology, researchers in Sweden found that concussion (brain injury) between the ages of 11 and 20 is associated with a higher risk of MS — and individuals who have had more than one concussion have an even higher risk of developing MS than those who have only had one.While there’s more to be learned about the connection between MS and concussion, the researchers commented that their results emphasized the importance of protecting young people from head injuries.