Multiple sclerosis is a chronic disabling disease of the central nervous system. During a sufferer’s lifetime, MS usually waxes and wanes until it progressively takes its toll over time. Although it is not fully understood, nerve fibers (axons) are highly implicated in the disease, where MS patients show some nerve fiber loss early in onset until it becomes the more predominant feature later in life. It is also known that inflammation within the central nervous system, perhaps triggered by an autoimmune effect, plays a hand in the destruction of nerve fibers.
While we tend to cover the vitamin D connection in multiple sclerosis on this blog, there are several environmental factors that researchers are studying that seem to be implicated in MS.
Recently, Dr Cullen O’Gorman and colleagues out of Australia took a look at this subject with this broader perspective. Here are the epidemiologic factors in MS, which may contribute to the incidence and progression of MS:
Genetic susceptibility. Genetic differences in the “Major Histocompatibility Complex” seem to put some at higher risk for MS. This complex is involved in the interaction of white blood cells with other cells all over the body. Whether this is just a coincidence or at the root of MS is unknown at this time.
Smoking. Studies show a general increased risk in those that smoke, with a recent meta-analysis reporting 48% increased risk of smokers getting MS. Furthermore, those who are “genetically susceptible” and smoke show a substantially increased risk.
It is also known that smoking increases the progression of MS. The reason for this could be a variety of reasons. It is generally known that smoking worsens many autoimmune diseases, probably by increasing inflammation and harming the immune system.
Low exposure to sunlight. Presumed to be related to vitamin D insufficiency. When looking at MS from a global perspective, the incidence of MS tends to be higher as you move away from the equator, with very high rates in Scandinavian countries. Furthermore, when migrants who move from high-prevalence MS regions to low-prevalence MS regions, the rates for the migrants drop. As most know, this observation has sparked intense interest in vitamin D and whether it might have a role in MS.
The active form of vitamin D has been shown to modulate nerve fiber loss and “remyelinate” the nerve fibers, myelins being essential to a healthy nervous system. Vitamin D also has a modulatory effect on inflammation that may be involved in MS. Thus, there is some thought that vitamin D can aid in treatment of MS.
There is some thought that genetics involved with vitamin D metabolism may also play a hand in the risk of MS.
Epstein-Barr Virus (EBV). EBV, while being asymptomatic in childhood, becomes problematic in adulthood, causing infectious mononucleosis (IM). Studies consistently report a two-fold increase in risk of MS in those with a history of IM.
However, there is little evidence that EBV causes MS, and it could be the case that vitamin D is at the root of both MS and EBV, though there is little research to date that supports this either.
As researchers scramble to discover more about the disease, prevention campaigns have been lacking. For treatment, most drugs used in the management of MS focus on suppressing the immune system, to help suppress the inflammation, in theory. While this has been somewhat clinically effective, these drugs have not been shown to decrease inflammation of the nervous system in MRI scans.
Given such, looking at epidemiologic factors and some of the possible mechanisms involved in the onset and progression of MS is important moving forward. Fortunately, trials are underway putting vitamin D to the test in trying to slow progression of the disease. Such trials cannot be performed for factors like EBV or smoking, placing all the more importance on vitamin D and MS research.