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Smoking Blamed for One-Third of Severe RA Cases

Rheumatoid arthritis risk is dependent on the amount of smoking and genetic predisposition

MONDAY, Dec. 20 (HealthDay News) -- Smoking is a preventable risk factor for rheumatoid arthritis, with risk dependent on the amount of smoking and genetic predisposition, according to a study published online Dec. 13 in Annals of the Rheumatic Diseases.

Henrik Källberg, M.D., of the Karolinska Institutet in Stockholm, Sweden, and colleagues evaluated data from the Swedish Epidemiological Investigation of Rheumatoid Arthritis case-control study, including 1,204 cases and 871 controls, to determine the association between the amount of smoking and risk of RA in the context of different HLA-DRB1 shared epitope alleles, and to estimate the proportion of RA attributed to smoking.

The investigators found that 61 percent of patients with RA had the most severe form of the disease, as indicated by testing positive for anticitrullinated protein/peptide antibody (ACPA), with those smoking 20 cigarettes a day for at least 20 years more than 2.5 times as likely to test positive for ACPA. While the risk for testing positive for ACPA decreased among ex-smokers, the risk was still relatively high for the heaviest smokers, even after 20 years of not smoking. The investigators calculated that smoking accounted for 35 percent of ACPA positive cases, and one in five cases of RA. Smoking accounted for 55 percent of cases involving genetic susceptibility to the disease and a positive test for ACPA, with the heaviest smokers at the highest risk.

"In conclusion, the data presented in this paper on the impact of smoking on the development of RA warrant more active information on the association between smoking and RA to the general public as well as to relatives of patients with RA," the authors write.

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