Lung function improvement following smoking cessation in chronic respiratory conditions: A meta-analytic approach

Introduction Smoking is a major contributor to the development and progression of chronic respiratory diseases. Although cessation is known to improve general health, its direct impact on pulmonary function remains debated. This meta-analysis aimed to evaluate the effects of various smoking cessation interventions on lung function outcomes in patients with chronic respiratory diseases. Methods A systematic search of PubMed, Scopus, and Web of Science was conducted to identify eligible clinical trials. Standardized mean differences with 95% confidence intervals were calculated to compare changes in forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and the FEV1/FVC ratio. Results Fourteen studies were included in the study. Smoking cessation was associated with a marginal improvement in FEV1 (standardized mean difference = 0.23; 95% confidence interval: −0.00 to 0.47; P = 0.054). However, no significant effects were observed on FVC (standardized mean difference = 0.08; 95% confidence interval: −0.17 to 0.23; P = 0.53) or the FEV1/FVC ratio (standardized mean difference = 2.26; 95% confidence interval: −2.25 to 6.78; P = 0.32). Subgroup analyses indicated that participant age may influence the heterogeneity of FEV1 outcomes. Conclusion Smoking cessation may be associated with small, nonsignificant changes in FEV1 and shows no significant short-term effects on FVC or the FEV1/FVC ratio. Although these results highlight the modest short-term impact of cessation on lung function, particularly in patients with established disease, they do not negate the substantial long-term clinical benefits of smoking cessation, including reductions in exacerbations, disease progression, and mortality.