African-Americans who smoke heavily – defined as at least a pack-a-day habit for at least 10 years – double their risk of getting rheumatoid arthritis, or RA, according to one study. On the flip side, researchers say about one in six new cases of RA in African-American patients could be avoided if they stopped or significantly limited their cigarette smoking.

“I think the big news is that smoking appears to be associated with development of RA in African-Americans. It’s something we’ve known in Caucasian and European populations for a while, but we’ve not really known this in African-Americans,” explains study author Ted Mikuls, MD, of the University of Nebraska Medical Center in Omaha. “It was unclear whether there would be an association or how strong it would be and from our data the association is pretty robust.”

For this new study, published in Arthritis & Rheumatism, Dr. Mikuls and his research team analyzed 605 African-Americans with RA and 255 without it. They determined if participants were current or former smokers or had never puffed on a cigarette at all. They also assessed participants’ smoking exposure and tested them for a genetic risk factor for RA known as HLA-DRB1.

“It’s a genetic risk factor that deals with immunity, and it seems to be really closely linked to a specific autoantibody in RA patients,” Dr. Mikuls explains.

After analyzing the data, Dr. Mikuls and his research team discovered that RA patients were more likely to currently have a smoking habit or have had one in the past than the non-RA group. Fifty-four percent of RA patients were classified as heavy smokers; 35 percent of those without RA were heavy smokers.

“The message is: Smoking is not a great idea, and if we can limit or stop smoking in that population it will likely lead to reduced numbers of [RA],” Dr.  Mikuls says.

Forty percent of those in the RA group also had the genetic risk factor, compared with 23 percent of the control group. “For whatever reason, this particular change in that gene makes people more susceptible to RA, and if you throw smoking on top of that, their risk escalates even further,” Dr. Mikuls says.

Dr. Mikuls says this data makes it clear that smoking increases RA risk. It’s just not yet known why. “I think that’s an important question we need to continue to chase after,” he says. “If we can understand why smoking increases risk, we’d learn a lot about this condition, and maybe even different ways to treat it or prevent it.”

Until that day comes, Robert Katz, MD, a rheumatologist and professor of medicine at Rush University Medical Center in Chicago, says if you have a strong family history of RA, a conversation is in order with any relatives who smoke heavily.

Dr. Katz says this study adds to a growing body of evidence that smoking increases the risk of RA in a variety of populations. “I would say I’m satisfied it’s a fact,” Dr. Katz says. “This is on the basis of several different studies, and it’s also logical. It makes sense.”

But he’s not sure word has gotten to the vast majority of doctors and patients, and he hopes studies like this will change that.

“The reasons not to smoke are so obvious that it’s usually not brought up in the context of predisposition to developing RA in your family, but it should be,” Dr. Katz says. “If someone reading this article has RA and says, ‘Oh, my son smokes.’ They need to show him this article.”