Current Smoking Negatively Affects the Response to Methotrexate in Rheumatoid Arthritis in a Dose-responsive Way, Independently of Concomitant Prednisone Use

Objective. Current smoking reduces clinical response to several disease-modifying antirheumatic drugs. It is unknown if this is also the case for prednisone. We aimed to determine whether current smoking affects the clinical response to concomitant prednisone in a methotrexate (MTX)-based treatment strategy. Methods. In the CAMERA-II trial (isrctn.com identifier: 70365169), patients with early rheumatoid arthritis (RA) initiated an MTX-based strategy and were randomized to concomitant prednisone (MTX + pred) or placebo (MTX + PBO) for 24 months. Linear mixed modeling was performed with Disease Activity Score assessing 28 joints (DAS28) as the dependent variable, and strategy group and current smoking status as independent variables, correcting for relevant covariates. The interaction between current smoking and strategy was tested to find out whether the effect of current smoking on clinical response was different between the strategy groups with prednisone or PBO. Results. Current smoking was significantly associated with higher DAS28 over time (mean difference with nonsmokers 0.57 [95% CI 0.22-0.92, P < 0.01]). This association was not different between the strategy groups with prednisone or PBO (P = 0.73). The negative effect of current smoking on DAS28 was dose dependent. Conclusion. Current smoking in patients with early RA significantly reduces the clinical effect of an MTX-based strategy, independent of whether concomitant prednisone is used. This effect is dose dependent.