In a study of US veterans, cigarette smoking was shown to increase the expression of markers of inflammation as well as clinical measures of rheumatoid arthritis (RA) disease activity.

Current smokers had a significantly higher cytokine score compared with former or never smokers and significantly more cytokines that were positive compared with former or never smokers.

“Notably, the cytokines found to be elevated in current smokers were many of the molecules that have been most strongly implicated in RA disease pathogenesis,” including tumor necrosis factor (TNF)-alpha, interleukin (IL)-2, IL-6, IL-12, IL-12p70, and interferon (IFN) gamma, the researchers wrote online in Rheumatology.

Current smokers also had significantly higher levels of RA disease activity than never smokers did, with Disease Activity Scores in 28 joints (DAS28) levels of 4.6 versus 3.7. Former smokers had levels of RA disease activity (mean DAS28 3.9), significantly lower than those of current smokers and similar to those of never smokers. These results persisted on multivariable analysis.

It is widely recognized that cigarette smoking is a strong risk factor for the development of RA, but the relationship between smoking and disease activity in established disease has been less clear, the researchers noted.

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