Multiple sclerosis (MS) is a disease in which the immune system mistakenly attacks the myelin sheath (a fatty protective coating) that covers nerve fibers and foster communication between the brain and the body. The loss of the myelin sheath leads to nerve cell degeneration, and a range of disease symptoms.
The exact cause of MS is not known, although researchers believe multiple factors contribute to the development of the disease.
MS is considered an auto-immune disease. But it is not known what causes the immune system to mistakenly attack the myelin sheath, and myelin-producing cells called oligodendrocytes, to disrupt the transmission of nerve impulses. Research is ongoing into factors that activate or influence the workings of immune cells throughout the central nervous system.
A number of environmental factors may contribute to a person’s likelihood of developing MS, including:
MS is more prevalent in some geographical regions than others, with a highest disease prevalence found in countries of northern Europe, and throughout the northern U.S., southern Canada, New Zealand and southern Australia. The distance a person lives from the equator seems to correlate with a risk of developing MS, with more patients identified in regions that are farther from the equator.
Vitamin D is important for immune system health, and there appears to be a link between vitamin D deficiency and a person’s chances of developing MS. This deficiency could also explain differences in disease prevalence by geographic location, since people living closer to the equator are more exposed to sunlight year-round so their bodies produce more vitamin D.
Obesity is thought to contribute to MS because it promotes chronic low-grade inflammation, which can affect immune responses.