Smoking is Associated with Progressive Disease Course and Increased Progression in Clinical Disability in a Prospective Cohort of People with Multiple Sclerosis
The contribution of modifiable lifestyle factors to MS disease course has not been well studied. We conducted a prospective cohort study of people with MS in Southern Tasmania. Recruitment occurred from 2002 to 2004 with 78% (203/259) of eligible MS patients participating Smoking data were collected at baseline and six-monthly reviews. Clinical disability assessments were conducted annually in conjunction with a real time clinical notification system for relapses. After confounder adjustment, cumulative pack-years smoked after cohort entry was associated with an increase in longitudinal MSSS (p<0.001.). Similar results were found using a variety of statistical approaches or EDSS as a clinical outcome. The adverse association between smoking during follow-up and MSSS persisted after adjustment for a range of confounding factors including immunomodulatory treatment, education and fish intake. Smoking appeared associated with progressive rather than relapsing remitting disease in that those who smoked prior to MS onset were more likely to have a primary progressive than relapsing remitting course at onset (AOR 4.35 (1.79, 10.00). Smoking during the cohort period was not associated with relapse. Smoking was associated with an increased risk of changing to a secondary progressive course within the cohort follow up period, but this finding appeared partly due to smokers being of older age with longer disease duration. A better understanding of the mechanisms underlying smoking and multiple sclerosis, particularly progressive forms of the disease may provide new insights for the eventual goal of better treatment and prevention of multiple sclerosis.