Smoking increases the risk of multiple sclerosis in Queensland, Australia

There is growing evidence for the role of smoking in the aetiology of multiple sclerosis (MS). We have undertaken a large case-control study of smoking in MS and assessed this using a regression model. We have confirmed an association between increased risk of MS and smoking in Queensland, Australia, a region of intermediate risk for MS. The overall adjusted odds ratio was 1.9 (95% confidence interval 1.5–2.5) for ever smokers. There was no statistically significant difference in the risks for males and females. A number of potential mechanisms to explain this association have been postulated including direct and indirect (via vitamin D) effects on the immune system.