Smoking Fears for MS Patients

The researchers, based in Harvard Medical School and Massachusetts Medical School studied 1,465 patients between February 2006 and August 2007.

Participants in the study had an average age of 42 and had MS for an average of 9.4 years. A total of 780 (53.2%) of the patients had never smoked, 428 (29.2%) had smoked in the past, and 257 (17.5%) were current smokers. During follow-up, 7 never-smokers began smoking and 57 current smokers quit.

Those who smoke had significantly more severe disease at the beginning of the study in relation to disability scores and also in the analysis of MRI factors, the study found. It discovered too that current smokers were also more likely to have primary progressive MS, characterised by a steady decline in health, rather than relapsing-remitting MS.

A group of 891 patients was assessed over time to evaluate the rate of conversion from relapsing-remitting MS to secondary progressive MS. During an average of 3.34 years, 72 patients (20 of 154 smokers, 20 of 237 ex-smokers, and 32 of 500 never-smokers) experienced this progression.

"The conversion from relapsing-remitting MS to secondary progressive MS occurred faster in current smokers compared with never-smokers but was similar in ex-smokers and never-smokers," according to the authors.

Previous research has indicated the adverse effects of smoking on the progress of MS, the authors concluded. Hardly surprising given that the components of cigarette smoke are known to have toxic effects on brain and neural tissue; for example, cyanides, which have been associated with the destruction of nerve cells' myelin coating in animals.

"Other chemicals in smoke can compromise the blood-brain barrier or have immunomodulatory effects," the authors wrote. "Cigarette smoke increases the frequency and duration of respiratory infections, which have been linked to risk of MS and to the occurrence of MS relapses."

"In conclusion, the results of this large and in part prospective investigation support the hypothesis that cigarette smoking has an adverse effect on progression of MS as measured by clinical and MRI outcomes," they concluded.

"Although causality remains to be proved, these findings suggest that patients with MS who quit smoking may not only reduce their risk of smoking-related diseases but also delay the progression of MS."