Chronic obstructive pulmonary disease and diabetes mellitus: a bidirectional meta-analysis of risk and comorbidity burden.

AIMS: This meta-analysis evaluated the bidirectional association and comorbidity burden between COPD and diabetes mellitus. MATERIALS AND METHODS: MEDLINE, Embase, Scopus, Web of Science Core Collection, and the Cochrane Library were searched from inception to May 2026. Observational studies and Mendelian randomization studies reporting comparative association estimates or prevalence data for COPD and diabetes mellitus were included. Two reviewers independently screened studies, extracted data, and assessed risk of bias using Joanna Briggs Institute tools. Random-effects meta-analyses were performed using DerSimonian-Laird inverse-variance models for association estimates and logit-transformed models for prevalence estimates. RESULTS: Thirty-one studies met eligibility criteria. COPD was associated with higher odds of diabetes mellitus (11 studies; OR = 1.56; 95%CI, 1.37-1.79), and this association marginally persisted in adjusted analyses (OR = 1.39; 95 CI, 1.01-1.77). The pooled prevalence of diabetes mellitus among COPD patients was 17% (95%CI, 14%-21%), while type 2 diabetes mellitus prevalence was 16% (95%CI, 7%-29%). In reverse-direction analyses, diabetes mellitus was associated with increased COPD risk (12 studies; OR = 1.29; 95%CI, 1.12-1.47), but not in adjusted analyses (OR = 1.20; 95%CI, 0.82-1.57). The pooled prevalence of COPD among diabetes mellitus patients was 17% (95% CI, 14%-21%) and 19% among type 2 diabetes mellitus patients (95% CI, 11%-28%). CONCLUSION: This meta-analysis suggests bidirectional association between COPD and diabetes mellitus and substantial comorbidity burden, although certainty of evidence was very low because of observational evidence and substantial heterogeneity. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/PROSPERO/view/CRD420261413229, identifier CRD420261413229.