Smoking increases the risk of progression in multiple sclerosis: A cohort study in Queensland, Australia

Cigarette smoking has been associated with increased risk of progressive multiple sclerosis (MS). The effect of smoking status on risk and timing of disease progression in patients with MS in Queensland, Australia has not been established.

A clinical cohort of 646 cases (531 females, 115 males) were followed from first clinic attendance to onset of clinically determined progressive disease. Progression risk was analysed with gender, age, age of onset, exposure to disease modifying therapy, and smoking status as covariates in a Cox proportional hazards analysis.

There were significantly higher risks of secondary progressive disease in males (Hazard Ratio, HR 1.83, 95% CI: 1.3-2.7) and in ever smokers (HR 1.4, 95% CI: 1.0-2.0). Progressive disease occurred approximately 4years earlier in ever smokers. Smoking did not affect age of onset of primary progressive disease.

Cigarette smoking was associated with earlier onset of progressive disease in this large clinical cohort. For patients with relapsing-remitting disease, smoking cessation should be encouraged.