People who start smoking before age 17 increase risk for multiple sclerosis

People who start smoking before age 17 may increase their risk for developing multiple sclerosis (MS), according to a study released today that will be presented at the American Academy of Neurology's 61st Annual Meeting in Seattle, April 25 to May 2, 2009.

The study involved 87 people with MS who were among more than 30,000 people in a larger study. The people with MS were divided into three groups: non-smokers, early smokers (smokers who began before age 17), and late smokers (those who started smoking at 17 or older), and matched by age, gender, and race to 435 people without MS.

Early smokers were 2.7 times more likely to develop MS than nonsmokers. Late smokers did not have an increased risk for the disease. More than 32 percent of the MS patients were early smokers, compared to 19 percent of the people without MS.

"Studies show that environmental factors play a prominent role in multiple sclerosis," said study author Joseph Finkelstein, MD, PhD, of Johns Hopkins University School of Medicine, in Baltimore, MD, which conducted the study in collaboration with Veterans Affairs MS Center for Excellence. "Early smoking is an environmental factor that can be avoided."