A shingles outbreak can nearly quadruple the risk of developing multiple sclerosis (MS) in the following year, but the overall risks remain small, Chinese researchers reported Thursday. Viruses are thought to play a role in triggering MS, and herpes zoster virus, which causes shingles, is one of the viruses previously implicated. But the new results reported in the Journal of Infectious Diseases are the first to quantify the risk.
Multiple sclerosis is an autoimmune disease characterized by the destruction of the myelin sheaths that enclose nerves and prevent them from short-circuiting. The disease can have a broad range of symptoms, ranging from mild prickling and pain in the extremities to severe disability and death. The rate of MS varies widely around the globe, ranging from 2 cases per 100,000 to 150 per 100,000.
Shingles is an exceptionally painful, blistering skin rash caused by the herpes zoster virus, the same virus that causes chickenpox. In many patients who suffer chickenpox in childhood, the virus is not eradicated from the body, but lies dormant for years or decades, until it is prompted to start replicating by environmental conditions, stress or infectious diseases.
Epidemiologist Herng-Ching Lin of Taipei Medical University in Taiwan and colleagues studied 315,550 adults with herpes zoster and a control group of 946,650 healthy controls, tracking them for a year to monitor for the development of MS. After adjusting for family income and geographic region -- both of which are known to play a role in MS -- the researchers found that the group with herpes zoster outbreaks was 3.96 times more likely to develop MS than the control group. On average, MS developed about 100 days after the shingles episode.