Smoking Increases Risk for Multiple Sclerosis

Abstract & Commentary

Source: Riise T, et al. Smoking is a risk factor for multiple sclerosis. Neurology. 2003;61:1122-1124.

In this epidemiologic analysis of 22,312 individuals living in Norway, a total of 87 reported having developed multiple sclerosis (prevalence rate, 390 per 100,000). Most patients with MS who were former smokers and all who were current smokers had started smoking before the onset of multiple sclerosis. The risk of developing multiple sclerosis was significantly higher among smokers than among never-smokers (rate ratio, 1.81; 95% CI, 1.1-2.9; P = .014). This was higher than the relative risk of smoking for stroke (rate ratio, 1.48; 95% CI, 0.94-2.35).


This study validates our clinical anecdotal observations about smoking and multiple sclerosis and identifies an important environmental variable that can be controlled to reduce the risk of multiple sclerosis in a person’s lifetime. A previous prospective study of a large cohort of female nurses showed an increased frequency of MS in smokers in a dose-dependent fashion.1 This dose-response relationship from Riise and associates’ study is still in analysis. Nonetheless, it is reasonable to expect that smoking is a significant comorbidity in the onset and disease severity of multiple sclerosis. Patients with multiple sclerosis should be strongly counseled to stop smoking. — Brian R. Apatoff, Associate Professor of Neurology, New York Presbyterian Hospital- Cornell Campus; Assistant Editor, Neurology Alert.


1. Hernan MA, et al. Am J Epidemiol. 2001;154:69-74.