Cigarette smoking and an Epstein–Barr virus infection together represent a significant risk factor for multiple sclerosis (MS), suggesting that at least one path to this disease involves two factors working synergistically, a study reports.
The study, “Smoking and Epstein–Barr virus infection in multiple sclerosis development,” was published in the journal Nature Scientific Reports.
Among the environmental factors associated with a likelihood of MS are smoking and infectious mononucleosis, caused by the Epstein–Barr virus (EBV).
However, previous studies into how smoking might interact with different aspects of EBV infection have reported conflicting results.
A team led by researchers at the Karolinska Institutet used two Swedish population-based case-control studies, involving 6,340 MS patients and 6,219 matched healthy people as controls, to investigate the interplay between smoking and EBV infection on the risk of this disease.
These two studies were the Epidemiological Investigation of Multiple Sclerosis (EIMS) and Genes and Environment in Multiple Sclerosis (GEMS), composed of people ages 16 to 70.
Participants in both studies answered a questionnaire regarding lifestyle factors and environmental exposures, and provided blood samples. Based on self-reported information, they either had a history of infectious mononucleosis or they did not.
Blood tests were to identify the presence of antibodies that target EBV, called EBNA-1 antibodies. Based on their results, patients were classified as having either high or low levels of EBNA-1. The presence of a gene variant associated with MS risk, known as DRB1*15:01, was also determined by genetic analysis.
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