TY - JOUR T1 - The effect of smoking on exacerbation risk in eosinophilic patients with COPD JF - European Respiratory Journal JO - Eur Respir J DO - 10.1183/13993003.01820-2017 VL - 50 IS - 6 SP - 1701820 AU - Christian R. Osadnik AU - Martin I. MacDonald AU - Philip G. Bardin Y1 - 2017/12/01 UR - http://erj.ersjournals.com/content/50/6/1701820.abstract N2 - We read with interest the findings of Kerkhof et al. [1], demonstrating an increased exacerbation risk in eosinophilic patients (eosinophil counts ≥0.45×109·L–1) with chronic obstructive pulmonary disease (COPD). When compared to a normal reference group (eosinophil counts of between 0.05 and 0.45×109·L–1), the rate ratios (RR) for exacerbations in the following year were lower in current smokers (RR=0.86) than in ex-smokers (RR=1.32). This finding is counter-intuitive and contrasts with data from large studies that demonstrate exacerbation reductions in COPD patients who cease smoking [2, 3]. A suppressive effect of active tobacco smoke on eosinophils is proposed as an explanatory mechanism by the authors; however, we feel the impact of potential confounders on this study finding should first be excluded prior to accepting this rationale.Higher exacerbation risk in COPD ex-smokers could reflect higher prior exacerbation history http://ow.ly/TbwP30fJNGj ER -