Introduction Smoking has consistently been associated with increased risk of developing rheumatoid arthritis (RA). The aim of this study was to estimate the influence of passive smoking on the risk of developing anti-cyclic citrullinated peptide antibodies (ACPA)-positive and ACPA-negative RA.
Methods A population-based case–control study using incident cases of RA was performed in Sweden, and the study population in this report was restricted to include never-smokers (589 cases, 1764 controls). The incidence of RA among never-smokers who had been exposed to passive smoking was compared with that of never-smokers who had never been exposed, by calculating the OR with a 95% CI employing logistic regression.
Results No association was observed between exposure to passive smoking and RA risk (OR 1.0, 95% CI 0.8 to 1.2 for ACPA-positive RA, and OR 0.9, 95% CI 0.7 to 1.2, for ACPA-negative RA). No suggestion of a trend between duration of passive smoking and RA risk was observed.
Discussions No association was observed between exposure to passive smoking and RA risk, which may be explained by a threshold below which no association between smoke exposure and RA occurs.
- rheumatoid arthritis
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Handling editor Josef S Smolen
Contributors Conception and design of the study, and acquisition of data: LA and LK. Analysis of data and drafting of the manuscript and tables: AKH. All authors revised the manuscript for important intellectual content.
Funding The EIRA study was supported by grants from the Swedish Medical Research Council, the Swedish Council for Health, Working life and Welfare, King Gustaf V:s 80-year foundation, the Swedish Rheumatism Foundation, Stockholm County Council, the insurance company AFA and the IMU-supported BeTheCure projects.
Competing interests None declared.
Patient consent Not required.
Ethics approval The ethics committee of the Karolinska Institutet.
Provenance and peer review Not commissioned; externally peer reviewed.
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