Abstract
Background: Obstructive sleep apnoea (OSA) and type 2 diabetes mellitus (T2DM) are common chronic conditions with a potentially bidirectional relationship mediated by insulin resistance, intermittent hypoxia, and systemic inflammation. However, evidence linking OSA with glucose dysregulation remains inconsistent. Objective: To evaluate the association between OSA and glucose dysregulation, including prediabetes and T2DM, and related metabolic and cardiovascular outcomes. Methods: A PRISMA-based systematic review was conducted using major databases. Results: In total, eleven studies from Asia, Europe, Africa, and South America were included in this review. The results show that OSA was consistently associated with poorer glycemic control, increased insulin resistance, and adverse metabolic profiles, with several studies demonstrating severity-dependent effects. In addition, poor sleep quality and short sleep duration were also linked to adverse metabolic outcomes, although findings were less consistent. Finally, limited evidence suggested that continuous positive airway pressure (CPAP) therapy may improve some metabolic and renal outcomes. Conclusion: OSA is consistently associated with impaired glucose metabolism and increased cardiometabolic risk in individuals with T2DM. Further longitudinal and interventional studies are needed to clarify causal pathways and the metabolic effects of OSA treatment. Systematic review registration: PROSPERO (CRD420261402284).