Smoking is a risk factor for multiple sclerosis.

The authors determined the relationship between tobacco smoking and the risk of developing multiple sclerosis (MS) in a general population of 22,312 individuals living in Hordaland, Norway in 1997. A total of 87 individuals reported having developed MS. The risk of MS was higher among smokers than among never-smokers (rate ratio 1.81, 95% CI 1.1 to 2.9; p = 0.014). Studies on how smoking interacts with disease onset may contribute to determining the causal agents of this disease.