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

IntroductionSmoking 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.MethodsA 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.ResultsFourteen 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.ConclusionSmoking 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.