Multiple sclerosis: cloudy winter days, more relapses

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MunichWinter is particularly troubling for people with multiple sclerosis: The lack of light provokes new attacks of their disease. We now also know why.

It has long been known that people who live in sun-drenched regions are less likely to develop multiple sclerosis. A large international study has now also confirmed a connection between the autoimmune disease and light. It shows that the sun protects people who are already sick from new attacks.

The team around Dr. Tim Spelmann from the Royal Melbourne Hospital evaluated the data from 10,000 MS patients from 30 countries. The subjects participated in the observational study for an average of eight years. In total, the scientists were able to evaluate information on 32,000 MS attacks - and when they had occurred over the course of the year.

The thrusts come later at the equator

The result: most of the flare-ups occurred at the end of winter or at the beginning of spring, but very few in autumn. The closer those affected lived to the equator, the later the relapses occurred - that is, more towards spring. And the less sun a patient could soak up on in winter, the sooner and more likely a flare-up would come.

The scientists suspect that the sun vitamin D has a positive effect on the course of the disease. Vitamin D is formed in the skin when exposed to UV light. The vitamin D level therefore reaches its highest level at the end of summer and then slowly decreases.

Stop misdirected immune cells

An American study had already shown in an experiment with mice that vitamin D prevents destructive immune cells from entering the brain. This prevents them from attacking the protective myelin layer of the nerve fibers and leading to symptoms of an MS attack such as paralysis, movement disorders, pain or visual disturbances.

“The higher the natural UV radiation, the lower the likelihood of relapses,” comments Heinz Wenzl from the German Society for Neurology. However, the doctor does not believe that the effect can be attributed to the vitamin D alone. "The effect of light on the immune system goes well beyond what we can explain with increased vitamin D production," says the expert. Accordingly, it would only help those affected to a limited extent to take vitamin D capsules.

First in episodes, later chronically

Multiple sclerosis is an autoimmune disease in which the body's immune defenses are misdirected and nerve cells are destroyed. In over 80 percent of patients, the symptoms initially appear relapsing. An MS flare-up can last from days to weeks. It usually takes at least 30 days before the next wave of symptoms occurs. The disease cannot be cured, but its course can be alleviated with medication. (away)

Source: Spelman T. et al .: Seasonal variation of relapse rate in multiple sclerosis is latitude dependent, Annals of Neurology, October 20, 2014.

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