Mon 27 October, 2003 21:05
Smokers are up to three times as likely to develop multiple sclerosis than nonsmokers, researchers said on Monday.
Researchers at the University of Bergen in Norway and Harvard University in Massachusetts surveyed 22,000 people aged 40 to 47 from 1997 to 1999 and found the risk of developing multiple sclerosis nearly three times higher for men who smoked and about two times higher for women smokers than for their nonsmoking counterparts.
"Cigarette smoke is a cocktail of chemicals that are potentially neurotoxins," said Alberto Ascherio, a researcher at the Harvard School of Public Health, who worked on the study.
However, when asked specifically how smoking triggers the disease, Ascherio responded, "Honestly we don't know. That is why this data is important." He said more research is needed.
The researchers found that most of the 87 people in the study who had multiple sclerosis started smoking 15 years before they developed the incurable disease. Of the multiple sclerosis patients, nearly 24 percent had never smoked and about 76 percent were current or past smokers.
"In order to be classified as smokers, they had to smoke at least one cigarette a day, and the number of years of smoking, in the total study population, ranged from one to 38," Trond Riise, who led the Bergen arm of the study, said in an interview conducted by e-mail.
It was not clear why male smokers had a higher rate of MS than women, Ascherio said.
The study will be published in the Oct. 28 issue of Neurology, the scientific journal of the American Academy of Neurology.
'Tell Them to Stop Smoking'
"Putting all the studies together, I feel pretty confident to say that, at this point, smoking increases the risk of multiple sclerosis," Ascherio said.
Gary Franklin at the University of Washington School of Public Health and Community Medicine in Seattle said the effect of smoking on multiple sclerosis was not extremely high.
"It's not like the relative risk of smoking and lung cancer," where people are three to five times more susceptible of getting the cancer if they smoke, he said.
However, Franklin, who wrote an editorial accompanying the study, continued, "if I had a patient who was maybe at risk for MS because someone else had it in the family, ... and were smoking, I'd probably tell them to stop smoking."
Stephen Reingold, vice president for research programs at the National Multiple Sclerosis Society, said smoking is one factor that could trigger multiple sclerosis in people genetically susceptible to developing it.
"The disease is not caused by smoking," Reingold said. "When we think about MS, we think about genetic factors and we think about risk co-factors that may be infectious, possibly environmental, and, as in the case of this, behavioral."
One of the most common neurological diseases in young people, multiple sclerosis disproportionately affects young women of northern European heritage, according to the American Academy of Neurology.
In a previous study, Ascherio found that one in about 200 women in the United States risk developing the disease, in which immune cells mistakenly attack and destroy myelin, the fatty material that insulates nerve fibers.
Common symptoms include vision loss, numbness, fatigue and paralysis.
MS is not fatal but can seriously disable patients.
Copyright © 2003, Reuters