Review Finds Strong Associations Between Cigarette Smoking and MS

Findings of a review analyzing the association between cigarette smoking and multiple sclerosis (MS) highlight numerous detrimental effects the habit has on those with the disease.

The review, published in the Journal of the America Medical Association (JAMA) Neurology, collected data from studies published between 1965 and 2018.

By taking the results of all the included studies into consideration researchers found, “patients with MS who smoke have higher rates of disease activity, faster rates of brain atrophy, and a greater disability burden.” Studies measured both the duration and intensity of the habit in patients with MS.

With over 2 billion consumers worldwide, and 5.8 trillion cigarettes consumed each year, risks associated with smoking cigarettes are experienced on a global level. Importantly, smoking cigarettes is more prevalent among patients with MS than the general population.

MS, which is a “chronic neurologic disorder characterized by demyelination and axonal loss in the central nervous system,” is often impacted by environmental factors, such as smoking. In addition to exacerbating the symptoms and ailments accompanying the disease, researchers found smoking cigarettes can limit the effectiveness of disease-modifying drugs.

Also, patients who smoke can see their MS progress more quickly. “Smoking has been shown to accelerate brain atrophy rates in the early disease stages, including in patients with clinically isolated syndrome (CIS),” the authors said. CIS is the earliest phase of MS.

Patients with MS tend to exhibit more comorbid disorders than the general population. Because smoking has severe implications on nearly every bodily system, comorbidities are exacerbated by the habit. “Smoking is implicated in the pathogenesis of other autoimmune disorders…patients with MS who smoked were more likely to develop another autoimmune disorder,” the authors said.

Despite the negative consequences, studies have found that patients with MS use smoking cigarettes as a coping mechanism. For this reason, patients often fail to quit. Unsuccessful attempts to quit smoking also lead to increased stress levels and have been associated with depression in patients with MS.

To combat the many negative impacts smoking has on patients with MS, researchers stress the importance of effective cessation mechanisms, one of which is counseling.

They state, “the increase in mortality rates appears to decrease after smoking cessation, which highlights the need for counseling…counseling is key in supporting patients before and during smoking cessation.”

The authors explain that physicians should expressly convey the benefits of quitting smoking to patients in a nonjudgmental manner and should be aware of the effect withdrawal may have on patients with MS.

Though the review focused specifically on the effects of smoking cigarettes on patients with MS, the authors suggest future studies look into associations between other detriments and the disease. One limitation present in multiple studies was the ambiguous definition of "passive smoking" adopted by researchers. This oversight led to discrepancies in findings. Future studies should also look into the associated consequences resulting from e-cigarette use.

“The pathway of MS pathogenesis in smokers may provide additional insights in the biologic factors associated with MS. Furthermore, the pathways involved in smoking may be implicated in other environmental exposures (e.g. organic solvents) and health habits (e.g. waterpipe smoking),” researchers concluded.

Reference

Rosso M, Chitnis T. Association between cigarette smoking and multiple sclerosis [published online December 16,2019]. JAMA Neurol. doi: 10.1001/jamaneurol.2019.4271.