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Original Contribution
July 2009

Smoking and Disease Progression in Multiple Sclerosis

Author Affiliations

Author Affiliations: Department of Neurology, Partners MS Center (Drs Healy, Ali, Guttmann, Chitnis, Glanz, Buckle, Houtchens, Moodie, Bakshi, Khoury, and Weiner and Ms Stazzone), Center for Neurological Imaging, Department of Radiology (Drs Guttmann, Berger, Duan, and Bakshi), and Channing Laboratory, Department of Medicine (Dr Ascherio), Brigham and Women's Hospital, Harvard Medical School; Biostatistics Center, Department of Neurology, Massachusetts General Hospital (Dr Healy); and Departments of Epidemiology and Nutrition, Harvard School of Public Health (Dr Ascherio), Boston, Massachusetts.

Arch Neurol. 2009;66(7):858-864. doi:10.1001/archneurol.2009.122

Background  Although cigarette smokers are at increased risk of developing multiple sclerosis (MS), the effect of smoking on the progression of MS remains uncertain.

Objective  To establish the relationship between cigarette smoking and progression of MS using clinical and magnetic resonance imaging outcomes

Design  Cross-sectional survey and longitudinal follow-up for a mean of 3.29 years, ending January 15, 2008.

Setting  Partners MS Center (Boston, Massachusetts), a referral center for patients with MS.

Patients  Study participants included 1465 patients with clinically definite MS (25.1% men), with mean (range) age at baseline of 42.0 (16-75) years and disease duration of 9.4 (0-50.4) years. Seven hundred eighty patients (53.2%) were never-smokers, 428 (29.2%) were ex-smokers, and 257 (17.5%) were current smokers.

Main Outcome Measures  Smoking groups were compared for baseline clinical and magnetic resonance imaging characteristics as well as progression and sustained progression on the Expanded Disability Status Scale at 2 and 5 years and time to disease conversion to secondary progressive MS. In addition, the rate of on-study change in the brain parenchymal fraction and T2 hyperintense lesion volume were compared.

Results  Current smokers had significantly worse disease at baseline than never-smokers in terms of Expanded Disability Status Scale score (adjusted P < .001), Multiple Sclerosis Severity Score (adjusted P < .001), and brain parenchymal fraction (adjusted P = .004). In addition, current smokers were significantly more likely to have primary progressive MS (adjusted odds ratio, 2.41; 95% confidence interval, 1.09-5.34). At longitudinal analyses, MS in smokers progressed from relapsing-remitting to secondary progressive disease faster than in never-smokers (hazard ratio for current smokers vs never-smokers, 2.50; 95% confidence interval, 1.42-4.41). In addition, in smokers, the T2-weighted lesion volume increased faster (P = .02), and brain parenchymal fraction decreased faster (P = .02).

Conclusion  Our data suggest that cigarette smoke has an adverse influence on the progression of MS and accelerates conversion from a relapsing-remitting to a progressive course.