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Many people know that multiple sclerosis (MS) is a long-term health condition that affects the central nervous system. However, it might come as a surprise that MS is more common in some parts of the world than others. Studies on the epidemiology of MS — how the disease affects different groups of people — show it’s more common the farther a place is from the equator.
MS is an autoimmune disease that damages the protective coating around nerve fibers, which can make it harder for the brain to send signals to the rest of the body. Researchers believe MS develops due to a mix of factors, including genetics, immune system activity, and the environment.
Geography — specifically, where someone lives — was one of the first environmental clues linked to MS. Other environmental factors that may raise the risk of MS include smoking, vitamin D levels, and exposure to certain viruses. Scientists are still figuring out how these pieces fit together, but they have a few ideas about the patterns they’re seeing.
This article explores which countries have the highest MS prevalence rates (number of people living with MS) and why that might be.
According to the National Multiple Sclerosis Society, MS is most common in areas farthest from the equator. Data from the Global Burden of Disease Study 2021 confirms that MS rates differ depending on how far north or south a country is. The highest rates of MS are found in Northern Europe — Sweden, Norway, the United Kingdom, and Ireland — and Canada.
The United States also has a high prevalence of MS. However, even within the U.S., MS is more common in northern states like Utah and Montana than in southern states such as Texas and Hawaii. This trend shows how MS tends to be less common closer to the equator.
The lowest rates of MS have been reported in sub-Saharan Africa and parts of Oceania — particularly in island nations such as Fiji, Guam, Samoa, and Tonga. However, other countries in the region, including Australia and New Zealand, have higher prevalence rates. Overall, MS appears to be more common in higher-income countries farther from the equator.
That said, some researchers warn that MS may be undercounted in parts of the world with limited access to medical care or record-keeping, including parts of Africa, Asia, and Oceania.
The MS International Federation’s Atlas of MS map shows updated estimates of where MS is most and least common around the world. These numbers can vary based on how complete the data is.
Differences in MS rates don’t just appear between countries — they also show up within them. Like the U.S., for example, Australia has varying rates. People living in southern areas like Tasmania are nearly twice as likely to develop MS as those living in northern areas such as Queensland. This north-south pattern has persisted over time, suggesting that environmental factors may influence MS risk even within the same country.
Where someone lives during childhood may also affect their risk for MS. Research shows that moving to a new location can change a person’s risk of MS — especially if they move before puberty.
If someone moves from a low-risk area near the equator to a higher-risk area farther away before age 15, their risk of MS becomes similar to the risk of people who grew up in the new location. The reverse is also true: Moving from a high-risk to a low-risk area may lower a person’s MS risk.
Neurology researchers believe that several geography-related factors may help explain why a diagnosis of MS is more common in some parts of the world than others.
In general, the farther a place is from the equator, the colder the climate. MS is more common in areas with bigger seasonal temperature changes than in tropical regions with warmer, more stable weather.
Temperature alone likely isn’t a cause of MS, but it may influence other risk factors. For example, one theory suggests that viruses linked to MS — such as Epstein-Barr virus (EBV) — might spread more easily in colder places. In colder weather, people tend to spend more time indoors and in close contact with others, which could increase the spread of viruses. In warmer climates, people often spend more time outside and may be less likely to pass infections to others.
More research is needed to fully understand how temperature and viruses might interact to affect MS risk.
Vitamin D is made in the body when skin is exposed to sunlight. This nutrient is important for bone health, immune function, and brain health.
People who live closer to the equator often have higher natural levels of vitamin D because they get more sun exposure year-round. According to the National Multiple Sclerosis Society, having high enough vitamin D levels may help lower the risk of MS.
Some evidence suggests that vitamin D supplements may help improve MS symptoms for some people, but results have been mixed. For example, a 2025 study found that high doses of vitamin D reduced disease activity in people with early-stage relapsing-remitting MS (RRMS) or clinically isolated syndrome. However, another study found that adding high-dose vitamin D to interferon beta-1a didn’t increase remission rates after 48 weeks compared with a placebo, which is an inactive treatment. Placebos are used in studies to show whether a treatment works better than taking the same treatment without the added active ingredient.
Scientists don’t yet know exactly how vitamin D helps protect against MS. However, vitamin D deficiency is one of the most strongly linked environmental risk factors for the disease.
What people eat — and what foods are available where they live — may also influence MS risk.
Some studies suggest that people who live near the ocean eat more fish, which is rich in omega-3 fatty acids and vitamin D. These nutrients may help reduce inflammation and may lower the risk of MS.
For example, a study in Norway found that between 1963 and 1983, people who lived in coastal regions and ate more fish had lower rates of MS than those living inland and eating less fish. A newer study from Sweden in 2025 found that people with MS who ate more fish had slower changes in their disability over six months.
Researchers haven’t proved that eating lots of fish prevents MS, but regional diets may help explain some of the connection between geography and MS risk.
MS is more common in certain parts of the world, but geography alone doesn’t determine who will develop the condition. Research shows that MS risk is shaped by a mix of genetic and environmental factors.
Scientists believe that interactions between a person’s genes, immune system, and environment all play a role. Researchers continue to explore how these factors work together — and may one day lead to ways to prevent MS.
If you’re living with MS, talk with your neurologist or another healthcare provider about MS treatment options that may be right for you.
On MyMSTeam, people share their experiences with multiple sclerosis, get advice, and find support from others who understand.
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You're forgetting one very important factor also associated with MS rates: UV light exposure. UV does more than produce vitamin D in the body; it also increases Regulatory T Cells (T-Regs)-- an… read more
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