Possible Causes of Multiple Sclerosis
The cause of multiple sclerosis (MS) is currently unknown. What we do know suggests that there isn't one single reason why someone gets MS. Instead, there are probably a number of different reasons, or factors, including both genetic and environmental factors. There is a genetic link to MS, but it is not directly inherited like some other conditions. It isn't caused by one faulty gene. Research into the genetics of MS has found over 100 genetic variations that may play a role in MS. But not everyone who has these genetic variations will get MS. MS can occur more than once in a family. A parent, sibling, or child of someone with MS has a 1 to 4 percent chance of having MS. More distant relatives have a risk closer to that of the general population, which is 0.1 to 0.5 percent (1-2 people per one thousand people).
While there is a genetic part to MS, it is not the whole story. Several environmental factors have been found. For instance, we know that MS is more common the farther you are from the equator. This suggests there's something in the environment related to distance from the equator that plays a role in MS. This something may be levels of vitamin D. Growing evidence shows that low levels of vitamin D before birth or during childhood may raise someone's chances of developing MS. Vitamin D is made by our skin when exposed to sunlight. People who live closer to the equator tend to have more exposure to the sun.
Other research about environmental causes of MS shows that common childhood viruses may have a role to play in MS. An example is the Epstein Barr virus. Smoking and passive smoke-exposure raise the risk of developing MS. People with MS who smoke are more likely to have worsening MS symptoms. They progress to secondary-progressive MS at a faster rate. They have greater risk of increasing disability. It's not yet clear exactly why this is. One theory is that the chemicals in tobacco smoke affect the immune system. If you are a smoker, consider joining the VA smoking cessation program. It's healthier for you and for others, especially children in your home. Finally, heart disease risk factors like high blood pressure, high cholesterol, and diabetes are all linked with worse outcomes in MS. It's important for people with MS to reduce these risk factors with good diet, regular exercise, and close care with their primary care doctors.
While some brain diseases, such as amyotrophic lateral sclerosis (ALS), have been linked with military deployment, this relationship has not been seen with MS.
