Health

Possible Link To MS

By CBSNews.com staff CBSNews.com staff

December 26, 2001 / 8:17 AM EST / CBS

New research finds there may be a link between a common virus and multiple sclerosis, reports CBS News Correspondent Tom Foty.

Epstein Barr sometimes causes mononucleosis, and researchers at Harvard report that women who show signs of having been exposed to the virus — even those likely exposed as children — appear to have a much higher chance of developing multiple sclerosis, as much as four times as great as women without the exposure.

But the researchers caution the correlation does not mean that Epstein Barr causes MS, a very serious nerve illness.

The virus, a member of the herpes family, also has been linked to other ailments, including some other nerve disorders and cancers, and is so common that by some estimates it has infected as many as 95 percent of U.S. adults by age 40.

Most exposure to the virus probably occurs in childhood, when there may be no symptoms, but antibodies to the germ would remain into adulthood, said Dr. Alberto Ascherio of Harvard's School of Public Health.

Coupled with previous research showing that people without Epstein-Barr antibodies rarely develop multiple sclerosis, the findings are "strong evidence in favor of a link," said Ascherio, lead author of the study in Wednesday's Journal of the American Medical Association.

However, Dr. Donald Gilden, author of a JAMA editorial and a University of Colorado neurologist, said that while MS probably is caused by a virus, Epstein-Barr probably isn't the culprit. He said blood tests such as those used in the study are not useful in determining cause and effect.

Nicholas LaRocca of the National Multiple Sclerosis Society said the study shows "a statistical association but not anything that you could really pin down as being causal or anything that really identifies a mechanism."

About 350,000 Americans have MS, a nerve disease that causes varying degrees of symptoms including numbness, muscle weakness and sometimes paralysis.

It is thought to be an autoimmune disorder, meaning the body's own disease-fighting immune system mistakes normal tissue as foreign. In MS, a protective nerve-fiber coating called myelin comes under attack. Previous research has suggested that viruses may trigger the autoimmune response in diseases like MS.

One problem with such studies is that it's unclear which came first — exposure to the virus or multiple sclerosis. LaRocca said determining when MS begins is difficult because symptoms may appear after the disease process has begun.

Ascherio says he sought to avoid that dilemma by studying women who had blood tests as much as 6½ years before they developed MS.

The authors examined blood samples taken from 62,439 women who participated in a Harvard-based nurses' health study beginning in 1989. The women gave blood samples in 1989-90 and 1996-99 and were followed up through 1999.

Among them, 144 had multiple sclerosis, though most were thought to have developed the disease before heir blood tests. For each woman with the disease, two women without MS were randomly selected, matched by year of birth.

Of 16 women whose blood was taken before they developed MS, 15 had significantly elevated levels of Epstein-Barr antibodies, Ascherio said.

Results of the study of more than 200,000 nurses, in two groups starting in 1989 and 1976, have led to new findings about exercise, stroke and cancer, among other medical issues.