It’s no secret smoking cigarettes can cause serious health problems, but a new study published in JAMA Neurology has found that if a smoker with multiple sclerosis (MS) doesn’t quit, they may worsen their disease. The results add to a growing body of research suggesting smoking cigarettes accelerates MS progression.

For the study, the research team looked at 728 Swedish smokers who were diagnosed with MS, a neurodegenerative disease that affects the central nervous system by disrupting the flow of information between the brain and rest of the body. MS patients typically start off at the relapsing-remitting stage of the disease, characterized by symptoms that come and go. It takes about 20 years for the disease to progress into secondary progressive (SP) disease, in which symptoms steadily worsen.

Of the participants, 332 continued to smoke after they were diagnosed. The researchers found that in these participants, the disease progressed into SP 4.7 percent faster for each year after an MS diagnosis that a patient smoked.

"This study adds to the important research demonstrating that smoking is an important modifiable risk factor in MS," wrote Dr. Myla D. Goldman, from the University of Virginia, and Dr. Olaf Stüve, from the University of Texas Southwestern Medical Center, in an editorial on the study. "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."

According to the National Multiple Sclerosis Society, there is mounting evidence showing how smoking can worsen a person’s MS progression. Studies, such as one from 2003, published in the journal Neurology, have also shown that smoking itself is a risk factor for developing MS, when compared to people who never smoke. Experts still aren’t exactly sure what causes MS in the first place, but they believe it’s triggered by a combination of environmental factors in people who are genetically predisposed to the disease.

Smoking is known to cause shortness of breath, susceptibility to lung infection, and heartbeat irregularities, which may be why it speeds along the progression of intermittent MS into the severe and debilitating SP stage. Aside from its role in MS, The U.S. Surgeon General recognizes smoking can also cause serious diseases in nearly all organs of the body, impair immune function, and reduce a person’s overall quality of life. If current rates of smoking continue, it’s estimated that 5.6 million Americans younger than the age of 18 will die prematurely from a smoking-related disease.

"This study demonstrates that smoking after MS diagnosis has a negative impact on the progression of the disease," wrote the study’s authors, from the Karolinska Institutet. "Accordingly, evidence clearly supports advising patients with MS who smoke to quit. Health care services for patients with MS should be organized to support such a lifestyle change."

Source: Hillert J. JAMA Neurology. 2015.