Smoking Increases Chances of Multiple Sclerosis in those with Epstein-Barr

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The Epstein-Barr virus is known to enhance the risk of multiple sclerosis. Researchers from the Harvard School of Public Health have found that smoking further increases that risk. The findings are published online in the April 7th issue of the journal Neurology.

Multiple Sclerosis is an incurable autoimmune disease that affects more than 400,000 people in the US and approximately 2 million people worldwide. It is caused by damage to the myelin sheath covering that surrounds nerve cells. The damage causes nerve impulses to slow or stop. MS is a progressive disease, meaning the neurodegeneration worsens over time. Previous research has found those diagnosed with MS who smoke are at higher risk for getting the brain lesions associated with the disease.

Kelly Claire Simon, ScD and colleagues used data from three case-control studies of multiple sclerosis (MS) – the American Nurses’ health Study/Nurses’ Health Study II, the Tasmanian MS Study in Australia, and a Swedish MS Study, representing a range of geographic diversity.

Within those databases, the researchers zeroed in on 442 patients with MS and compared them to 865 healthy controls. Those patients were stratified according to Epstein-Barr antibody levels. Those who had levels above the median who smoked had double the risk of developing MS.

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Another MS risk factor, an immune system related gene called HLA-DR15, did not show the same association.

Epstein-Barr virus, commonly referred to as EBV, is a member of the herpes virus family and one of the most common human viruses. In the US, as many as 95% of adults between the ages 35 and 40 years have been affected, according to the Centers for Disease Control and Prevention.

The authors do note that their study had limitations that need further research to clarify the interaction risk. For example, the study was limited by different exposure assessments, the research was not able to account for the changes over time in smoking behavior, and that few patients had antibody testing before their diagnosis of MS.

"Although higher antibody titers to EBV are associated with an increased risk of MS, an individual's absolute risk of MS associated with high antibody titers to EBV is still small," said Simon.

Source reference:
Simon KC, et al "Combined effects of smoking, anti-EBNA antibodies, and HLA-DRB1*1501 on multiple sclerosis risk" Neurology 2010; 74: 1-1.

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