A Retrospective Study on the Association of the Systemic Inflammatory Response Index in Predicting the Severity of Obstructive Sleep Apnea

<b>Background/Objectives:</b> Obstructive sleep apnea (OSA) is a common disorder characterized by intermittent hypoxia and sleep fragmentation, assessed using the Apnea-Hypopnea Index (AHI). Systemic inflammation is central to OSA progression, and the systemic inflammatory response index (SIRI) has emerged as a potential biomarker for inflammatory diseases. This study investigates the relationship between SIRI and OSA severity while comparing other inflammatory markers. <b>Methods:</b> A retrospective study was conducted among 150 OSA patients at a tertiary care hospital. Based on AHI, patients were categorized into mild, moderate, and severe OSA groups. Blood parameters, including neutrophil, monocyte, and lymphocyte counts, were analyzed, and inflammatory indices (SIRI, NLR, PLR) were calculated. Correlation, ROCs, and regression analyses assessed associations between inflammatory markers and OSA severity. <b>Results:</b> SIRI demonstrated an excellent predictive ability for severe OSA with an AUC of 0.960 (cut-off: 1.105; sensitivity: 92.2%; specificity: 91.4%). The STOP-BANG score alone had lower discriminatory power (AUC: 0.737), but combining it with SIRI improved accuracy (AUC: 0.983). The best performance was observed when SIRI, STOP-BANG, PLR, and CRP were combined, yielding an AUC of 1.00, indicating perfect discrimination. <b>Conclusions:</b> SIRI shows strong predictive value for identifying severe OSA, underscoring its utility as a simple, cost-effective biomarker to aid early recognition and referral, particularly in primary care and resource-limited settings.