Background Smoking has consistently been associated with increased risk of developing rheumatoid arthritis (RA). However, no studies have been performed investigating the effect of exposure to environmental tobacco smoke (i.e. passive smoking) on RA risk.
Objectives The aim of this study was to estimate the influence of passive smoking on the risk of developing the two major subsets of RA, defined by anti-citrullinated protein antibodies (ACPA) status.
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 odds ratio with a 95% confidence interval employing logistic regression.
Results No association was observed between exposure to passive smoking and RA risk (OR 1.0, 95% CI 0.8–1.2 for ACPA positive RA, and OR 0.9, 95% CI 0.7–1.2 for ACPA negative RA). No suggestion of a trend between duration of passive smoking and RA risk was observed.
Conclusions 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.
Acknowledgements 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, the EU-supported AutoCure and BeTheCure projects, and from the COMBINE (Controlling chronic inflammatory diseases with combined efforts) project.
Disclosure of Interest None declared