RT Journal Article SR Electronic T1 Smoking as a risk factor for the radiological severity of rheumatoid arthritis: a study on six cohorts JF Annals of the Rheumatic Diseases JO Ann Rheum Dis FD BMJ Publishing Group Ltd and European League Against Rheumatism SP annrheumdis-2013-203940 DO 10.1136/annrheumdis-2013-203940 A1 D P C de Rooy A1 J A B van Nies A1 M C Kapetanovic A1 H Kristjansdottir A1 M L E Andersson A1 K Forslind A1 D M F M van der Heijde A1 P K Gregersen A1 E Lindqvist A1 T W J Huizinga A1 G Gröndal A1 B Svensson A1 A H M van der Helm-van Mil YR 2014 UL http://ard.bmj.com/content/early/2014/01/03/annrheumdis-2013-203940.abstract AB Background Smoking is a risk factor for the development of anti -citrullinated protein antibodies (ACPA) positive rheumatoid arthritis (RA). Whether smoking predisposes to severe joint damage progression is not known, since deleterious, protective and neutral observations have been made. Objective To determine the effect of smoking on joint damage progression. Methods Smoking status was assessed in 3158 RA patients included in six cohorts (Leiden Early Arthritis Clinic (Leiden-EAC), BARFOT, Lund, Iceland, NDB and Wichita). In total 9412 radiographs were assessed. Multivariate normal regression and linear regression analyses were performed. Data were summarised in a random effects inverse variance meta-analysis. Results When comparing radiological progression for RA patients that were never, past and current smokers, smoking was significantly associated with more severe joint damage in Leiden-EAC (p=0.042) and BARFOT (p=0.015) RA patients. No significant associations were found in the other cohorts, though a meta-analysis on the six cohorts showed significantly more severe joint damage progression in smokers (p=0.01). Since smoking predisposes to ACPA, analyses were repeated with ACPA as additional adjustment factor. Then the association was lost (meta-analysis p=0.29). Conclusions This multi-cohort study indicated that the effect of smoking on joint damage is mediated via ACPA and that smoking is not an independent risk factor for radiological progression in RA.