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Smoking and MS

Smoking is a major lifestyle issue for those who seek optimal health, but there is now evidence of its specific detrimental effects in MS. Smoking, with all its harmful effects on the body, has a role in MS development. An important point to emerge from a large study on nurses’ health was the very clear association between cigarette smoking and multiple sclerosis.1  The Nurses’ Health Study found that, compared with women who had never smoked, the risk of getting MS was 1.6 times greater for current smokers, and 1.2 times greater for past smokers. There was also a clear relationship between the duration of smoking and risk of MS. The risk was highest (1.7 times) for those who had smoked for over 25 years. This was supported by a Norwergian smoking MS study which showed a very similar risk, with smokers 1.8 times more likely to develop MS than non-smokers.2
Now there are enough reasons for anybody to give up smoking even without this data. With all the serious health problems smoking causes, from heart disease and lung cancer through to a range of other cancers, the single biggest positive health decision any smoker can make is to quit the habit. But for people with MS, or if MS runs in the family, there are even more compelling reasons to give up. This study didn’t look at whether smoking worsens existing MS, just at whether it is associated with its development, but a more recent smoking MS study has examined the issue of how smoking influences MS progression. Researchers at Harvard School of Public Health conducted a well designed case-control study on smokers with MS.3 People with MS who had ever smoked were 3-4 times more likely to develop secondary progressive MS than those who had never smoked. A Swedish smoking MS study in 2008 confirmed in a group of 122 people with MS for a mean duration of six years, that smokers were significantly more likely to have progressive disease, and to progress at an earlier age.4

A French case-control smoking MS study showed that children were more than twice as likely to get MS if their parents smoked, and the longer they were exposed, the more likely MS was to develop.5 So passive smoking is harmful in MS as well. Another smoking MS study from Austrian researchers published in 2008 showed that for people who had had an initial attack suggestive of MS, smokers were nearly twice as likely to go on and develop definite MS, and to develop it earlier than non-smokers.6 This has important implications for relatives of people with MS. Both passive smoking in the household and active smoking by as yet unaffected relatives make the development of MS more likely. A 2009 report from Johns Hopkins University presented to the AAN meeting in Seattle noted that those who started smoking earlier, in their study, before the age of 17, were considerably more likely to develop MS.

Unfortunately, studies have shown more people with MS smoking than in the general population.7 Smoking is an important potential modifier of the progression of MS. For people with MS who still smoke, this strong evidence means that making a positive choice about giving up smoking for better health in general is likely to favourably affect the course of MS as well. It is a reasonably simple lifestyle change which can make a great difference to disease progression.
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  1. Hernan MA, Oleky MJ, Ascherio A. Cigarette smoking and incidence of multiple sclerosis. Am J Epidemiol 2001; 154:69-74.
  2. Riise T, Nortvedt MW, Ascherio A. Smoking is a risk factor for multiple sclerosis. Neurology 2003; 61:1122-1124
  3. Hernan MA, Jick SS, Logroscino G, et al. Cigarette smoking and the progression of multiple sclerosis. Brain 2005
  4. Sundstrom P, Nystrom L. Smoking worsens the prognosis in multiple sclerosis. Mult Scler 2008
  5. Mikaeloff Y, Caridade G, Tardieu M, et al. Parental smoking at home and the risk of childhood-onset multiple sclerosis in children. Brain 2007; 130:2589-2595
  6. Di Pauli F, Reindl M, Ehling R, et al. Smoking is a risk factor for early conversion to clinically definite multiple sclerosis. Mult Scler 2008
  7. Nortvedt MW, Riise T, Maeland JG. Multiple sclerosis and lifestyle factors: the Hordaland Health Study. Neurol Sci 2005; 26:334-339