A new study involving people with MS who smoked cigarettes suggests that those who continued to smoke after receiving an MS diagnosis were quicker to reach the secondary-progressive phase of MS than those who quit after diagnosis.
Those who continued to smoke converted to secondary-progressive MS at a median age of 48, while those who quit smoking within the year after MS diagnosis progressed at a median age of 56.
This adds to evidence that smoking may speed progression of MS, and offers new evidence that quitting smoking after MS diagnosis may slow progression.
The team (Ryan Ramanujam, PhD, Jan Hillert, MD, PhD, and colleagues at Karolinska University Hospital Solna, Stockholm, Sweden) has published results in JAMA Neurology (Published online September 8, 2015). The full paper is available free of charge.
Background: In most people, MS begins with a relapsing-remitting course with defined attacks of worsening neurologic function, followed by periods of partial or complete recovery. Most people eventually transition to secondary-progressive MS, where the disease begins to progress or worsen more steadily, with or without relapses. The factors that determine if or when a person may transition to secondary-progressive MS are not fully understood. Some studies have found that smoking is related to disease progression, and that MS disability progresses more quickly in smokers, but the impact of quitting after diagnosis had not been thoroughly determined.
The Study: Investigators identified 728 people with MS who smoked at the time of MS diagnosis and were enrolled in the large Genes and Environment in MS Study in Sweden. Of these, 332 were classified as “continuers” who smoked at least one cigarette per day continuously from the year after diagnosis and 118 were considered “quitters,” who had stopped smoking within the year after diagnosis. A group of 278 were “intermittent smokers” but were not included in the final evaluation.
The main focus of the study was to determine how smoking was related to conversion to secondary-progressive MS, which occurred in 216 people. The researchers found that each year of smoking after diagnosis accelerated the time to conversion to secondary-progressive MS by 4.7%. Continuers progressed to secondary-progressive MS faster (at a median age of 48) compared with quitters (age 56).
Results were published in JAMA Neurology (Published online September 08, 2015). The full paper is available free of charge.
Comment: This is an important study that adds to evidence that smoking speeds progression of MS, and offers new evidence that quitting smoking after MS diagnosis may slow progression. In an accompanying editorial, Drs. Myla D. Goldman (University of Virginia, Charlottesville) and Olaf Stüve (University of Texas Southwestern Medical Center at Dallas) comment that this may be the first evidence that quitting smoking can delay conversion to secondary-progressive MS. “Therefore, even after MS diagnosis, smoking is a risk factor worth modifying,” they write.
The National Institutes of Health provides resources to help quit smoking: visit smokefree.gov or call 1-800-QUITNOW (1-800-784-8669).