Nicotine might have a protective effect in the etiology of multiple sclerosis

Objective: The use of moist snuff is common in Sweden and leads to exposure to high doses of nicotine. Recent studies indicate that exposure to nicotine could modulate immune responses. The aim of this study was to investigate the influence of snuff use on the risk of developing multiple sclerosis (MS), taking smoking habits into consideration. Methods: In two Swedish population-based, case-control studies (7883 cases, 9437 controls), subjects with different snuff use habits were compared regarding MS risk, by calculating odds ratios (ORs) with 95% confidence intervals (CIs). Results: Snuff-takers have a decreased risk of developing MS compared with those who have never used moist snuff (OR 0.83, 95% CI 0.75-0.92), and we found clear evidence of an inverse dose-response correlation between cumulative dose of snuff use and the risk of developing the disease. We further observed that subjects who combined smoking and snuff use had a significantly lower risk for MS than smokers who had never used moist snuff, also after adjustment for amount of smoking. Conclusions: Our results add evidence to the hypothesis that nicotine exerts anti-inflammatory and immune-modulating effects in a way that might decrease the risk of developing MS.