Smoking May Speed Up MS Disease Course

September 10, 2015

Continuing smoking after a diagnosis of multiple sclerosis (MS) appears to be associated with accelerated disease progression, a new study suggests.

"Evidence clearly supports advising patients with MS who smoke to quit," the authors, led by Ryan Ramanujam, PhD, and Jan Hillert, MD, Karolinska Institutet, Stockholm, Sweden, conclude. "Health care services for patients with MS should be organized to support such a lifestyle change."

In an accompanying editorial, Myla D. Goldman, MD, University of Virginia, Charlottesville, and Olaf Stüve, MD, PhD, University of Texas Southwestern Medical Center at Dallas, write, "This study adds to the important research demonstrating that smoking is an important modifiable risk factor in MS. Most importantly, it provides the first evidence, to our knowledge, that quitting smoking appears to delay onset of secondary progressive MS and provide protective benefit. Therefore, even after MS diagnosis, smoking is a risk factor worth modifying."

The study and editorial were published online September 8 in JAMA Neurology.

The cross-sectional study included 728 patients with MS who smoked and 1012 patients with MS who did not smoke. They were identified from a Swedish national MS registry, and patient environmental data were collected via questionnaire.

Among the 728 smokers, 332 were classified as "continuers" who smoked at least one cigarette per day continuously from the year after diagnosis and 118 were "quitters" who stopped smoking the year after diagnosis. The other 278 were intermittent smokers who were not considered in the primary outcome.

In a comparison of those who continued smoking to those who gave up, results suggested that patients who continued to smoke after diagnosis converted to secondary progressive MS at a younger age (48 years) than those who quit (56 years).

This corresponds to 4.7% acceleration in time to onset of secondary progression (P = .006).

"The primary finding of reduced time to onset of secondary progressive MS is in line with other findings and offers encouragement for patients with MS to abstain from cigarette smoking," the editorialists write.

They point out, however, that when they compared patients who smoked at the time of initial MS diagnosis to those who had never smoked, there was no difference in the age at conversion to secondary progressive MS. In trying to explain this, Dr Ramanujam and colleagues suggest that prediagnosis smoking may affect risk but not disease course, which, the editorialists note, "has been suggested by the work of others."

Dr Goldman and Dr Stüve also point out that the current study did not look at whether smoking reduction would be beneficial, as their broad classification for continued smoking (at least one cigarette a day) prevented any examination of dose effect. "Thus, it remains unclear whether simply cutting back on the amount one is smoking could provide any benefit."

They also note that while the groups were well balanced across most measures, there was one notable difference: the time from diagnosis to treatment. Both the never-smokers and the quitters had shorter time to treatment than did those who were smokers at diagnosis and the continuers.

"This more than 12-month difference in the start of treatment is a potential confounder in the difference seen in age at time of secondary progressive MS onset," they state.

This study was supported by grants from Neuroförbundet, the Swedish Research Council, The Knut and Alice Wallenberg Foundation, the AFA foundation, the Swedish Brain Foundation, Margareta af Ugglas Stiftelse, EU FP7 Neurinox, the Bibby and Nils Jensen Foundation, and the Karolinska Institutet Research fund. Dr Hillert has received honoraria for serving on advisory boards for Biogen and Novartis and speakers fees from Biogen, Merck-Serono, Bayer-Schering, Teva Pharmaceuticals, and Sanofi. He has served as the principal investigator for projects sponsored by or has received unrestricted research support from Biogen, Sanofi, Merck-Serono, Teva Pharmaceuticals, Novartis, and Bayer-Schering.

JAMA Neurol. Published online September 8, 2015. Abstract Editorial


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.