Smoking & Rheumatoid Arthritis:

Smoke gets in your joints?

Dr Chris Deighton, NRAS Medical Advisor, Consultant Rheumatologist at Derbyshire Royal Infirmary and President Elect of British Society for Rheumatology
Original article: 30/05/2008
Reviewed: 05/02/2010
Next review due: 05/02/2013

Some of you may recall an old song called “Smoke gets in your eyes”. Nobody will remember an editorial I wrote over ten years ago for the Annals of the Rheumatic Diseases entitled “Smoke gets in your joints?” The reason why the title had a question mark was because the possible link between smoking and RA was controversial. Is the picture any clearer twelve years later?

Huge and important questions about the cause of RA remain unanswered. Work on identical twins suggests that genetics may account for just over half of the total weight of factors in the cause of RA. However, there is still a large gap for other non-inherited factors that lead some people to develop RA. The environment in and around us must interact with genetic factors to push some people’s immune systems into breaking-down, and resulting ultimately in RA.

Discovering these environmental factors has proven to be difficult. In Europe RA seems a relatively modern disease, becoming established over the past 200 - 300 years. Pollution and cigarette smoking are also modern epidemics. Populations exposed to pollution and cigarettes are much more prone to become positive for rheumatoid factor, the antibody that until recently was most strongly associated with RA (now overtaken by anti-CCP antibodies – see below). Not everybody who is positive for rheumatoid factor will develop RA, but it definitely raises the chances. Could tobacco smoke influence the immune system in genetically susceptible individuals, and raise the chances of RA?

Some very important recent studies from the famous Karolinska Institute in Sweden have suggested such interactions might take place. These studies showed that cigarette smoking might change some of the components of proteins in the lungs, and then could generate the production of anti-CCP antibodies. These antibodies have been shown to be much more predictive of RA than rheumatoid factors, and may precede the onset of RA by many years. Furthermore, the production of anti-CCP antibodies is strongly determined by the presence of the same genetic factors that predispose to RA. Overall the risk of RA in smokers is two to four times that in non-smokers.

Swedish colleagues were able to show that if you had inherited two copies of the genes that most strongly predispose to RA, and were a smoker, and were positive for anti-CCP antibodies, then the risks of developing RA were a huge 21 times greater than the risk for the rest of the population.

Other studies from Holland and Denmark have shown remarkably similar observations. However, just to prove that studies in RA are never completely in agreement, a study of North American RA populations failed to show these strong associations. These discrepancies between European and American studies might be because of differences in proportions of heavy smokers, but also raise the possibility that different risk factors may be more important than others in different parts of the world. The important message for UK RA patients is that European studies suggest that interactions between smoking, genes and anti-CCP antibodies might load the dice strongly in favour of developing RA.

A number of studies have suggested that if people continue to smoke after developing RA, they are more likely to develop more severe joint disease, and RA disease outside joints such as rheumatoid nodules, and inflammation in blood vessels known as vasculitis.

Stopping smoking after developing RA is therefore a great idea, because it might mean that your joint disease might not be as bad as it would have been if you had continued to smoke. Furthermore, people with RA are more prone to furring of the arteries (atherosclerosis), and resultant heart disease, and cigarette smoking only serves to aggravate this further.

What lessons do we need to learn from all of this?

• If the nation stopped smoking, RA would become less common.
• There are many good reasons to stop smoking that have nothing to do with RA (e.g. heart and lung disease). The fact that RA itself increases the risk of heart disease means it is even more important to stop smoking. But there are also good reasons to stop that have much to do with your joints. It is a great way to help yourself in managing your disease.
• If you do not want to stop smoking for yourself, then stop smoking for your other family members. They might have inherited the same genetic factors to RA as you have, and inhaling your cigarette smoke might increase their chances further.
• Every rheumatology department should reinforce the message that smoking is bad for RA, and should have help available to allow people to stop. If they do not, then show them this article and complain!

References available on request