Can environmental factors cause multiple sclerosis (MS)?

Epidemiologists, scientists who study disease patterns, have learned that multiple sclerosis (MS) occurs more frequently in geographic locations that are farther from the equator. In an effort to understand the puzzling disease patterns found in MS, scientists continue to examine geographic, demographic, and genetic variables. For example, studies have shown that people born in a geographic location with a high incidence of MS, who move to a geographic location with a lower incidence of MS before the age of 15, will acquire the lesser risk associated with their new location. Such data suggest that exposure to some environmental factor or factors prior to puberty, such as diet, exposure to industrial toxins, or content in water or soil may predispose a person to develop MS later in life.

Some researchers believe vitamin D, which the body produces naturally when the skin is exposed to sunlight, may be involved. People who live closer to the equator are continually exposed to greater amounts of sunlight. As a result, they tend to have higher levels of naturally-produced vitamin D, which is thought to have a beneficial impact on immune function and may help protect against autoimmune diseases, like MS.