Although cigarette smokers have an increased risk of developing multiple sclerosis (MS), the effect of smoking on MS progression remains uncertain.
To establish the relationship between cigarette smoking and MS progression using clinical and MRI outcomes
Cross-sectional survey and longitudinal follow-up for an average of 3.29 years, ending January 15, 2008.
Partners MS Center (Boston, MA), a referral center for MS patients
1465 patients with clinically definite MS (25.1% men) with mean baseline age of 42.0 years (range: 16–75) and disease duration of 9.4 years (range: 0–50.4) -- 780 (53.2%) patients were never smokers, 428 (29.2%) ex-smokers, and 257 (17.5%) were current smokers.
Main Outcome Measures
Smoking groups were compared in terms of baseline clinical and MRI characteristics as well as progression and sustained progression on the expanded disability status scale (EDSS) at 2 years and 5 years and the time until conversion to secondary progressive MS. In addition, the rate of on-study change in the brain parenchymal fraction (BPF) and T2 hyperintense lesion volume was compared.
Current smokers had significantly worse disease at baseline than never-smokers in terms of EDSS (adjusted p<0.0001), multiple sclerosis severity score (adjusted p<0.0001), and BPF (adjusted p=0.004). In addition, current smokers were significantly more likely to have primary progressive MS (adjusted odds ratio=2.41; 95% CI: 1.09, 5.34). In longitudinal analyses, smokers converted from relapsing remitting MS to secondary progressive MS faster than never-smokers (HR for current smokers versus never smokers, =2.50, 95% CI: 1.42, 4.41) and had a faster rate of increase in the T2 lesion volume (p=0.017) and a faster rate of decrease in BPF (p=0.021).
Our data suggest that cigarette smoke has an adverse influence on MS progression and accelerates the conversion from a relapsing-remitting to a progressive course.