Researchers have long suspected that external factors may influence the risk for multiple sclerosis (MS), a chronic autoimmune disease that affects the central nervous system, according to background information in the article. Some studies have suggested that the Epstein-Barr virus, which affects up to 96 percent of Americans by the time they reach age 35 to 40 years, may play a role.
Gerald N. DeLorenze, Ph.D., Kaiser Permanente Division of Research, Oakland, Calif., and colleagues examined the records of patients who joined a health plan between 1965 and 1974, when they were an average of 32.4 years old. The patients had undergone multiple examinations, answered questions about their health and behaviors and submitted blood samples, which were processed and stored at cold temperatures. Between 1995 and 1999, the researchers searched medical records maintained by the health plan and selected 42 individuals with MS who had blood samples in storage. Three people with blood samples but without MS were matched to each MS patient by age, sex and date of blood collection. The blood samples of all participants were then analyzed to determine the levels of antibodies against the Epstein-Barr virus. Measuring antibodies, proteins produced by the body to fight infection, is one way to determine exposure to or presence of a particular virus in a person's body.
The 36 women and six men who developed MS had their first symptoms at an average age of 45 years and an average of 15 years after their blood was collected. The average concentration of anti-Epstein-Barr virus antibodies was significantly higher among individuals who had developed MS than among those who hadn't--those with four times the level of antibodies were approximately twice as likely to develop MS. The elevated levels became evident between 15 and 20 years before patients first experienced the neurological symptoms of MS and remained higher afterward, the researchers reported.
Researchers don't yet understand how the Epstein-Barr virus causes the body to attack its own central nervous system, as it does in MS. "The mounting evidence that relates Epstein-Barr virus infection to other autoimmune diseases, particularly systemic lupus erythematosus (lupus), suggests that Epstein-Barr virus may have a broad role in predisposing to autoimmunity," or failure of the immune system to recognize the body's own tissues, the authors conclude. "A fine understanding of the mechanisms that connect Epstein-Barr virus infection to MS is important because it will provide the basis for the translation of this epidemiologic finding into new ways to treat and prevent MS."