COPD-OSA overlap syndrome: inflammatory and oxidative stress mechanisms, biomarkers, and clinical implications.

COPD-OSA overlap syndrome is associated with a greater disease burden and poorer clinical outcomes than either condition alone. COPD-related chronic airway inflammation and OSA-related intermittent hypoxia may converge to promote oxidative stress, inflammatory activation, endothelial dysfunction, and multisystem injury. This narrative mechanistic review examines these pathways using evidence from overlap syndrome, COPD, OSA, and relevant preclinical studies. It also discusses candidate biomarkers of inflammation, oxidative stress, and endothelial injury, emphasizing their exploratory status and current limitations. Established disease-directed management, phenotype-informed supportive interventions, and investigational mechanism-based strategies are reviewed. A clearer understanding of the biological and clinical heterogeneity of overlap syndrome may facilitate risk stratification, refined phenotyping, and more individualized management.