How Does Environment Play a Role in MS?

Reviewed by: HU Medical Review Board

There is still much that is unknown about the causes of multiple sclerosis (MS). Researchers are exploring environmental factors that may contribute to the disease. Some possible factors include:1,2

  • Geographic location
  • Vitamin D deficiency
  • Obesity
  • Smoking
  • Chemicals and pollutants

The environment's role in MS

It is important to note that there is no single cause of MS. Rather, a mix of genes and environment most likely plays a part. Doctors are still working to learn all the factors, but it is clear that a person's environment plays an important role.1,2

MS clusters

There is some evidence that MS may be more likely to occur in areas with clusters of cases. This suggests something in the environment may be triggering the disease in these areas. MS clusters are hard to study. But they could provide needed information on the causes of MS.3


There appears to be a link between geography and MS. People who live in temperate climates are more likely to develop MS than those in tropical climates. Experts think this may be due to their levels of vitamin D.2,4

Vitamin D

Vitamin D is an essential nutrient that helps the body absorb calcium and maintain strong bones. You can find vitamin D in certain foods, such as fatty fish. It is also produced by the body when the skin is exposed to sunlight.1,2

People who live in sunny climates closer to the equator tend to have higher levels of vitamin D. This is probably because they are able to get more sunlight.2

Some studies have suggested that vitamin D deficiency may play a role in developing MS. Vitamin D might help regulate the immune system. So, a lack of vitamin D could lead to an autoimmune response. However, more research is needed to confirm this link.1,2


Obesity is a complex condition with many causes. Obesity in children and teenagers, particularly girls, has been linked to a higher risk of MS. According to some studies, obesity in early adulthood may also raise the risk of MS.2

It is unclear why obesity might raise the chance of developing MS. It may be because it changes the immune system's response. More research is needed to know whether there is a valid link between obesity and MS.2


Experts think smoking plays a role in MS. Cigarette smoke contains toxins that may damage the nervous system. Evidence suggests that smoking or exposure to secondhand smoke may increase the risk of MS and MS progression.2,4

Chemicals and pollutants

Exposure to pollutants such as metals and solvents has been linked to increased risk of MS. One theory is that these pollutants may damage the nervous system, leading to MS. However, more research is needed to confirm this link.2,4,5

Air pollution also has been linked to increased cases of MS. The exact effect of air pollution on MS is unknown. Doctors think that pollution leads to an abnormal immune response and inflammation in the body. These reactions may trigger MS.5

Researchers continue to study the connection between environment and MS. Currently, there is no evidence that any 1 factor is responsible. The environment, however, appears to be significant in the development of this disease.1,2,4

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