10 Multiple Sclerosis Risk Factors

Both genes and environment seem to play a role.

Multiple sclerosis is a condition with nuances surrounding it that continue to baffle experts. The condition causes your immune system to attack the sheaths covering your nerves—the myelin. Here are 10 risk factors that may increase your chances of developing MS:

According to Johns Hopkins Medicine, we know MS is a chronic autoimmune disease affecting the central nervous system. by attacking the myelin sheathing. This process causes damaging inflammation that interrupts the way the nervous system communicates with the rest of the body, leading to various symptoms.

Biological Sex

Montel Williams and a few other high-profile celebrities have been diagnosed with MS, but by and large, MS disproportionately strikes females, Nancy L. Sicotte, MD, said. And the gap between males and females is growing: "It used to be two women to every one man, but several new studies suggest that the ratio is approaching 4-to-1," Dr. Sicotte said.

Johns Hopkins Medicine explained researchers are unsure exactly why four times as many females have MS as males. However, they explained current theories center around hormones, body fat and obesity, and vitamin D levels.

In addition, even though the disease is more common among females (they are also more likely to get MS at a younger age), it tends to be more severe in men, John Rose, MD, professor of neurology at the University of Utah, said.

Where You Live

According to a review study published in 2019 in the journal Annals of Clinical and Translational Neurology, the prevalence of people diagnosed with MS increases the farther away you are from the equator.

It is thought that vitamin D, or lack thereof, is the reason. Our bodies produce D in response to sunlight, so people farther from the equator make less, especially during the long, dark winter months.

Environmental Exposures as a Child

According to the same review study published in 2019 in the journal Annals of Clinical and Translational Neurology, environmental exposures associated with the development of MS may occur before the age of 15 years. This is based on studies on migration.

The same study also mentioned exposure to maternal illness while in utero (other than diabetes and preeclampsia) and environmental exposures to the neonate (young infant), such as lower levels of vitamin D, that are thought to possibly play a role in the development of MS.

When You Were Born

A study published in 2016 in the journal JAMA Neurology examined the month of birth and subsequent diagnosis of MS among birth data in the UK (England, Wales, and Scotland) between 1938-2000. The authors controlled for other variables and found an increased risk of developing MS among persons born in April.

Conversely, of those born in November, 15.58% fewer individuals developed MS.

A possible explanation: "If your mother was pregnant with you through the winter, her levels of vitamin D during pregnancy might have been low," Dr. Rose said.

Your Ethnicity

According to a study published in 2020 in the journal Multiple Sclerosis, white individuals of European ancestry are most likely to develop MS. Hispanic and Asian individuals are less likely to develop the condition. The study examined several genetic variations, looking specifically at genetics in Hispanic, African, European, and Native American populations

Populations in northern latitudes generally have higher MS rates, according to the study. However, changes in what has been considered higher-risk populations are changing. For example, in the United States, there are currently increasing rates of MS in African Americans. Previously, there used to be a belief that African Americans were a lower-risk population.

Additionally, the study explained there have been increasing reports of Hispanic children diagnosed with MS. And individuals in the United States who identified as Hispanic developed MS on average 3-5 years sooner than those who identified as non-Hispanic white. Research is ongoing into the racial and ethnic differences in the onset and progression of MS.

Your Smoking Status

According to a study published in 2019 in the journal Annals of Clinical and Translational Neurology, smoking cigarettes is a well-known risk factor for developing MS. The thought is that the lung irritation and inflammation caused by smoking are the culprits.

However, the good news, according to the study, is that if you quit smoking, after ten years of not smoking cigarettes, your risk returns to your baseline risk. This means smoking cigarettes is a risk factor you can control by avoiding smoking or quitting.

Your Age

According to Johns Hopkins All Children's Hospital, you can be diagnosed with MS at almost any time, from childhood through older adulthood. However, a diagnosis is most likely between the ages of 20 to 50 years old.

"MS is not an all-comers' disease," Carrie Lyn Sammarco, DrNP, FNP-C, MSCN, said. "We don't tend to see it in children, although it can occur." Johns Hopkins All Children's Hospital explained that while uncommon, approximately 5% of MS diagnoses each year are in children.

Previous Mono Infection

Many germs have been studied as possible MS triggers, but the results have been mixed. There is, however, a growing body of evidence that Epstein-Barr virus (EBV) is correlated with subsequent MS diagnosis. EBV is the virus that causes mononucleosis or mono.

A study published in May 2020 in the Journal of Neurology, Neurosurgery, and Psychiatry collected blood samples from a sample size of 901 patients with an early MS diagnosis from the German National MS Cohort.

Every participant tested positive for EBV antibodies. The authors discuss the possibility of MS being a late-stage complication of EBV, with further research indicated.

Viral Infection and Genetic Expression

Triggers that may impact an individual's genetic risk for developing MS are an ongoing area of research. One study, published in 2019 in the journal Annals of Clinical and Translational Neurology, discussed how past infections with Epstein-Barr virus (the virus responsible for mono), and other viruses, may affect the development of autoimmune diseases, such as MS, through their effect on genetic expression.

The study stated that some individuals are more susceptible to developing MS. The genetic variations seen in those susceptible to MS are also seen across numerous other autoimmune conditions.

In fact, per the study, a protein from the Epstein-Barr Virus (called EBNA2) has been suggested to affect the future development of MS, as well as numerous other autoimmune conditions. These include systemic lupus erythematosus, type 1 diabetes, inflammatory bowel diseases, rheumatoid arthritis, juvenile idiopathic arthritis, and celiac disease. This is all due to genetic effects that are dependent on the EBNA2 protein.

Other viruses may have an association with the development of MS too. For example, the National Multiple Sclerosis Society explained that human herpes virus 6 (HHV-6) might be involved in MS. HHV-6 might be significantly involved in relapses of MS.

And a study published in 2017 in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) explained how infection with the common flu virus, influenza A, may be associated with relapses of MS.

While there are solid cases for the involvement of viruses (especially EBV) in the development of MS, per the National Multiple Sclerosis Society, researchers have not been able to pinpoint one virus that definitively causes MS.

Your Family History

While environmental factors impact your chances of developing this disease, so does your family history. "If a [parent] has MS, their children have between a 5 and 10 percent chance of getting it," Dr. Rose said.

Medline Plus explained that while the exact inheritance pattern is unknown, MS does appear to run in families. Per Medline Plus, those who have siblings or parents with MS are at a greater risk of developing the disease.


Overall, there are many possible risk factors for developing MS, which is a complex process. Very few risk factors are clear-cut, and variability exists depending on the research behind them.

If you're concerned you may have MS or are concerned about your own personal risk factors for MS, seeing a healthcare provider is a great place to start to determine if any next steps are needed.

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