Clinical characteristics and factors associated with one-year smoking cessation among smokers with COPD: a subgroup analysis of a multicentre randomised trial

Abstract

Background: Smoking cessation is the most effective intervention for modifying the clinical course of chronic obstructive pulmonary disease (COPD), yet many patients continue to smoke after diagnosis. We evaluated the characteristics associated with cessation at one year among smokers with COPD in a multicentre randomised cessation trial. Methods: This prespecified subgroup analysis included patients with COPD randomised to immediate referral to a smoking cessation clinic or to usual care. Smoking status one year later was determined through a structured telephone interview, and patients who had quit were contacted and their cessation was verified by exhaled carbon monoxide measurement; 48 of the 220 patients (21.8%) were lost to follow-up, leaving 172 patients for analysis. A prespecified six-variable logistic regression model was fitted; Firth penalised regression and an analysis classifying patients lost to follow-up as continuing smokers were prespecified sensitivity analyses. Results: Of 172 patients, 32 (18.6%) had quit at one year: 24 of 93 (25.8%) allocated to immediate referral versus 8 of 79 (10.1%) allocated to usual care (p = 0.010). Quitters were older and had a lower baseline FEV1 in unadjusted comparisons. In the multivariable model, usual care was associated with lower odds of cessation (OR, 0.25; 95% CI, 0.09–0.64), whereas absence of comorbidity (OR, 2.64; 95% CI, 1.06–6.60) and more than 1 exacerbation-related hospitalisation (OR, 9.32; 95% CI, 1.97–44.06) were associated with higher odds; the latter estimate rests on 10 patients and is imprecise. Baseline FEV1 and Fagerström score were not independently associated with cessation. Conclusion: Immediate referral to a cessation clinic was the factor most strongly associated with one-year abstinence, together with absence of comorbidity and, tentatively, repeated hospitalisation; greater disease severity was associated with quitting only in unadjusted comparisons. These exploratory findings support structured cessation pathways in routine COPD care.