The effect of smoking on exacerbation risk in eosinophilic patients with COPD

We read with interest the findings of Kerkhof et al. [1], demonstrating an increased exacerbation risk in eosinophilic patients (eosinophil counts ≥0.45x109·L–1) with chronic obstructive pulmonary disease (COPD). When compared to a normal reference group (eosinophil counts of between 0.05 and 0.45x109·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.
Source: European Respiratory Journal - Category: Respiratory Medicine Authors: Tags: COPD and smoking Original Articles: Correspondence Source Type: research