BOSTON — A variant in a gene involved in breaking down chemicals in smoke triples a smoker’s risk of multiple sclerosis, a study shows.
Smoking increases by 30 to 50 percent a person’s risk of multiple sclerosis, a disease in which the immune system attacks a waxy coating around nerve cells. Scientists don’t know exactly how smoking contributes to the disease.
Farren Briggs of the University of California, Berkeley and his colleagues searched DNA of thousands of people in Northern California, Norway and Sweden for genetic variants associated with both smoking and multiple sclerosis. The team found hundreds of variants in three genes involved in breaking down chemicals found in smoke, Briggs said October 24 at the annual meeting of the American Society of Human Genetics.
In particular, people who smoke and who have two copies of a variant in the NAT1 gene have a risk of getting MS that is three times higher than that of smokers without the variant. For nonsmokers, the variant doesn’t increase MS risk.