Cigarette smoking increases the relapse rate in patients with relapsing-remitting multiple sclerosis (RRMS) who are being treated with interferon-beta, a study suggests.
The findings suggest that RRMS patients who smoke may have fewer relapses if they quit.
An article on the results, “Smoking affects the interferon beta treatment response in multiple sclerosis,” appeared in the journal Neurology.
A number of studies have looked at the link between environmental and lifestyle factors and the risk of developing MS. These factors include how much sunlight and vitamin D patients get and whether they have an Epstein-Barr virus infection.
Cigarette smoking is a well-documented risk factor in MS, but most of the studies on it have focused on the link between smoking and MS, or the link between smoking and the disease’s progression.
“Studies that addressed the relationship between smoking and disease activity in RRMS are rarer,” the researchers wrote.
The team decided to investigate whether smoking during interferon-beta treatment would affect relapse rates.
Previous research had set the stage for the study by showing a link between smoking and gene mutations that make people more susceptible to developing MS. The mutations were in the HLA and NAT1 genes.
The team looked at DNA from 834 RRMS patients in the Danish Multiple Sclerosis Biobank who were treated with interferon-beta. Well-known brand names of the treatment include Rebif, Avonex, and Plegridy. There are also other brand names and biosimilar drugs.
Researchers also looked at patients’ medical records two years before they started on interferon-beta.
Before making any conclusions on possible links between smoking and patients’ relapse rate, the team adjusted for patients’ sex, age at the start of treatment, and number of relapses in the two years before treatment began.
Their key conclusion was that smoking increased by more than a quarter the number of relapses in patients on interferon-beta therapy.
“Each pack of cigarettes more per day during IFN-β [interferon-beta] treatment increased the number of relapses by 27%,” the team wrote.
The researchers found no association among smoking, relapses, and mutations of the HLA or NAT1 genes.
“Our results confirm that lifestyle factors are important in MS, suggesting that smoking cessation may be associated with a reduction in disease activity,” they wrote.
“Although not formally proving that smoking cessation will decrease disease activity in RRMS, the results should encourage physicians to inform patients with MS about the harmful effect of smoking and increase focus on smoking cessation,” they observed.