Cigarette smoking is a well-established risk factor for developing rheumatoid arthritis (RA), and previous research has shown that ever-smokers have a 40 percent higher risk of RA than never-smokers. Little is known however, regarding the dose-response relationship between the quantity of cigarette smoking and the risk of RA.
In a recent meta-analysis, researchers have found a non-linear dose-response trend. The risk of developing RA increased significantly with increasing number of pack-years (a unit of quantifying cigarette smoking, where a pack year is defined as smoking 20 cigarettes a day for one year). This correlation occurred up to 20 pack-years, after which the relative risk stabilised, even for those individuals who smoked more than 40 pack-years.
There appears to be a non-linear dose relationship between lifelong smoking and RA, with risk increasing up to 20 pack years.
Written by Stephanie Harriman, Deputy Medical Editor for BioMed Central.
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