In the 2009 population-based case-control study performed in Sweden, involving persons diagnosed with MS (n=902) and controls (n=1,855), the incidence of MS among smokers was compared with that of never-smokers.  Both women and men smokers were 40-80% more likely to develop MS (OR 1.4, 95% CI 1.2-1.7 for women, and OR 1.8, 95% CI 1.3-2.5 for men) with the increased risk associated with smoking remaining for up to 5 years after a person stopped smoking.  

In the 2009 study, persons who used Swedish snuff for more than 15 years had a 70% decreased risk of MS (OR 0.3, 95% CI 0.1-0.8) suggesting that nicotine may not be the substance responsible for the increased risk of developing MS among smokers (Hedström, 2009).  In fact, results from the current study, which was a follow-up to the original one in published in 2009, supports the hypothesis that nicotine exerts anti-inflammatory and immune-modulating effects in a way that might decrease the risk of developing MS (Hedström, 2013).

SOURCES:
Microbiology and Immunology Mobile - Immunology Chapter Thirteen: Cytokines and Immunoregulation. Accessed at http://pathmicro.med.sc.edu/mobile/m.immuno-13.htm

Hedström A, et al. Nicotine might have a protective effect in the etiology of multiple sclerosis. Mult Scler 2013 Jan 14. [Epub ahead of print]

Hedström A, et al. Exposure to environmental tobacco smoke is associated with increased risk for multiple sclerosis. Mult Scler 2011 Jul;17(7):788-93. doi: 10.1177/1352458511399610. Epub 2011 Mar 3.

Hedström A, et al. Tobacco smoking, but not Swedish snuff use, increases the risk of multiple sclerosis. Neurology 2009 Sep 1;73(9):696-701. doi: 10.1212/WNL.0b013e3181b59c40.

Cloëz-Tayarani I, Changeux JP. Nicotine and serotonin in immune regulation and inflammatory processes: a perspective. J Leukoc Biol 2007 81(3):599–606. doi: 10.1189/jlb.0906544

“Swedish Hopes Rise on Snus Ban” by Anna Molin, Wall Street Journal, October 21, 2012, accessed January 23, 2013.

Lisa Emrich is author of the blog Brass and Ivory: Life with MS and RA and founder of the Carnival of MS Bloggers.