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NEW YORK (Reuters Life!) - People who get shingles are more likely to also develop multiple sclerosis, with researchers in Taiwan finding that people who developed shingles had four times the risk of being diagnosed with MS within the next year.
But the team led by Jiunn-Horng Kang at Taipei Medical University Hospital warned that their study did not show that shingles itself could cause MS, although there were "several potential mechanisms" that could explain why the two diseases are linked.
"Our findings support the notion that occurrence of MS could be associated with herpes zoster attack," Kang and colleagues wrote in the Journal of Infectious Diseases.
"We found a significantly higher risk for MS within 1 year of (a) herpes zoster attack compared with the control population."
Shingles is a painful condition caused by reactivation of the virus that causes chicken pox, known as varicella-zoster virus. Once a person has had chicken pox, the virus goes into a dormant state, dwelling in the body's nerve fibers.
However, in some people the virus can reactivate and cause shingles, which usually begins with a burning pain or itch in one location on one side of the body, followed by a rash of fluid-filled blisters.
MS occurs when the protective coating around nerve fibers begins to break down, slowing the brain's communication to the rest of the body. Symptoms include fatigue and problems with balance and muscle coordination, as well as memory loss and trouble with logical thinking in some people.
About 2.5 million people have MS worldwide, according to the Multiple Sclerosis Association of America. Most experience their first symptoms between the ages of 15 and 50.
Reviewing a database from the insurer that covers 98 percent of Taiwan's population, the researchers found more than 300,000 people with shingles. They compared them to nearly 950,000 others with similar characteristics, who didn't have the disease.
Over the course of a year, fewer than one in 10,000 in the group with shingles developed MS -- but that was still nearly four times as many as in the group without shingles.
"After adjusting for monthly income and geographic region, the hazard of MS was 3.96 times greater for the study group than controls," the researchers wrote.
Kang said that shingles is associated with disruptions to the immune system, which in turn might trigger MS. Also, a reactivation of the shingles virus may "provoke a series of immune responses in the host which may be linked to MS," Kang told Reuters Health.
The authors cautioned that most people included in the study were Han Chinese, among whom MS occurs relatively infrequently, so the findings might not apply to Western populations.
In addition, the authors did not have information about whether people smoked or drank alcohol, another potential influence on the findings.
"These factors may be confounding to our results and need to be further explored," Kang added.
Reporting by Alison McCook; editing by Elaine Lies