Does Smoking Increase the Risk of
Co-existing Autoimmune Diseases in MS?


    Some studies have reported that persons with MS are more likely to have other autoimmune diseases (AD) than persons in the general population, but some studies have not.1,2 When two diseases occur together more often than expected, researchers consider why. One possible explanation is that the causes of the two diseases are the same. This means that comparing people with both diseases to people with only one of the diseases may help to identify the cause of those diseases.

    Smoking is a possible risk factor for MS and for autoimmune diseases including rheumatoid arthritis, inflammatory bowel disease (such as Crohn’s disease), and possibly uveitis (swelling in the eye). 3,4,5 We looked at whether smokers with MS were more likely to have a co-existing AD than non-smokers with MS.

Smoking was associated with a 43% increased risk of rheumatoid arthritis and 38% increased risk of uveitis


    In the Fall 2006 update questionnaire we asked NARCOMS participants whether they had other health problem in addition to MS.6  For each condition we asked what year the condition was diagnosed, and whether participants were receiving any treatment for the condition. The list of AD we asked about is shown below (Table 1).

    Dr. Marrie is a Don Paty Career Scientist and Director of MS Clinic at University of Manitoba Health Sciences Center in Winnipeg, Canada.
   She is a researcher and a practicing neurologist who will be sharing her knowledge with NARCOMS participants throughout the year.

    Most NARCOMS surveys contain some question about smoking status, but in Fall 2006 more in-depth questions were asked and then we classified each participant as “Ever Smoked” if they had indicated smoking 100 or more cigarettes or “Never Smoked” if they had smoked less than 100 cigarettes total.


    A total of 8,983 NARCOMS participants were included in the study.6 Of these 24% were men and 76% were women. Ninety-four percent were white, 2.4% were African American, and 3.3% reported another race. The average age of the responders was 52.7 years and 54% of them reported having smoked at some point.


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