Smoking is a known risk factor for developing rheumatoid arthritis, or RA, and research has shown smoking can reduce the efficacy of treatments. Now, new research adds more weight to the advice that RA patients shouldn’t light up: Smokers are 50 percent less likely to respond well to treatments in early RA than non-smokers, according to a study published in the January 2011 issue of Arthritis & Rheumatism.

“Smoking is a lifestyle habit that is modifiable, and the findings … give strong argument to include measures against smoking as part of RA care,” explains lead author Saedis Saevarsdottir, MD, PhD, a rheumatology fellow at the Karolinska University Hospital and postdoctoral researcher at the Karolinska Institute in Stockholm, Sweden.

To learn how cigarette smoking affected response to the most commonly used first- and second-line RA drugs – methotrexate and tumor necrosis factor (TNF) inhibitors – Swedish researchers analyzed data on more than 1,430 patients between 1996 and 2006. Of this group, 873 were taking methotrexate and 535 were taking anti-TNFs.

Three months after starting methotrexate, 27 percent of smokers responded well, compared with 36 percent of non-smokers. Of those on TNF inhibitors, such as infliximab, or Remicade, and etanercept, or Enbrel, 29 percent of smokers responded well after three months, compared with 43 percent of non-smokers.

 “We also evaluated whether the accumulated dose of cigarettes smoked, measured by pack-years (1 pack-year equals 20 cigarettes a day for 1 year) influenced the response in the smokers, which was not the case,” Dr. Saevarsdottir says.

Another reason to kick the habit: Former smokers responded just as well to RA treatments as those who never smoked.

Dr. Saevarsdottir says researchers hope this new information is detailed enough to encourage RA patients who are still smoking to stop.

“Possibly, the patients are more motivated to stop when the information is specific for their actual situation than when it is a general recommendation to the public as a whole,” Dr. Saevarsdottir says.

James O’Dell, MD, a professor of internal medicine and chief of the rheumatology division at the University of Nebraska Medical System in Omaha, says that while previous studies have linked smoking to not responding well to methotrexate, the information in this study about anti-TNFs is a newer observation.

“The most powerful message I want to get to anyone with RA is we’ve had many reasons for many years why smoking is uniquely bad for people with RA, and this is more evidence in that direction,” Dr. O’Dell says. “If I can tell people when they start their methotrexate that I have data they will have better chance to respond if they stop smoking – and if I can tell them the same thing when I start them on TNF inhibitors – that may give them another impetus to stop smoking.”

Dr. O’Dell says it is important to point out that patients in Sweden may be different from U.S. patients, and that observational studies, such as this one, aren’t definitive.

“There are lots of unseen things in observational studies we can’t correct for,” Dr. O’Dell says. “In general I think this is well done, but it’s not rock solid because there are always confounding variables when we are looking at observational data.”