Association of mild chronic obstructive pulmonary disease with all-cause mortality: A systematic review and meta-analysis

BackgroundIt is unclear whether patients with Global Initiative for Chronic Obstructive Lung Disease stage 1 (mild) chronic obstructive pulmonary disease (COPD) have worse respiratory outcomes than individuals with normal spirometry. MethodsFor this systematic review and meta-analysis, we conducted a search of PubMed, Embase, and Web of Science for all literature published up to 1 March 2023. Studies comparing mortality between mild COPD and normal spirometry were included. A random-effects model was used to estimate the combined effect size and its 95% confidence interval (CI). The primary outcome was all-cause mortality. Respiratory disease-related mortality were examined as secondary outcomes. ResultsOf 5242 titles identified, 12 publications were included. Patients with mild COPD had a higher risk of all-cause mortality than individuals with normal spirometry (pre-bronchodilator: hazard ratio [HR] = 1.21, 95% CI: 1.11-1.32, I-2 = 47.1%; post-bronchodilator: HR = 1.19, 95% CI: 1.02-1.39, I-2 = 0.0%). Funnel plots showed a symmetrical distribution of studies and did not suggest publication bias. In jackknife sensitivity analyses, the increased risk of all-cause mortality remained consistent for mild COPD. When the meta-analysis was repeated and one study was omitted each time, the HR and corresponding 95% CI were >1. Patients with mild COPD also had a higher risk of respiratory disease-related mortality (HR = 1.71, 95% CI: 1.03-2.82, I-2 = 0.0%). ConclusionsOur results suggest that mild COPD is associated with increased all-cause mortality and respiratory disease-related mortality compared with normal spirometry. Further research is required to determine whether early intervention and treatment are beneficial in mild COPD. (c) 2023 Sociedade Portuguesa de Pneumologia. Published by Elsevier Espa & ntilde;a, S.L.U. This is anopen access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).