The Role of the C-Reactive Protein-to-Albumin Ratio and Hematological Inflammatory Markers in Predicting the Severity of Obstructive Sleep Apnea Syndrome

INTRODUCTION: It is well established that systemic inflammatory responses induced by intermittent hypoxia are associated with disease severity in obstructive sleep apnea syndrome (OSAS). This study aimed to investigate the association between the C-reactive protein–to–albumin ratio (CAR), hematological inflammatory markers, and disease severity in OSAS, and to assess their diagnostic performance for predicting moderate-to-severe OSAS.
METHODS: We included 230 individuals aged 18–65 years who underwent full-night polysomnography in our sleep laboratory between June 2025 and December 2025. Participants were classified as normal, mild, moderate, or severe OSAS according to the apnea–hypopnea index (AHI). Serum C-reactive protein (CRP) and albumin levels were measured in all participants, and CAR, neutrophil-to-lymphocyte ratio (NLR), and systemic immune-inflammation index (SII) were calculated. Independent predictors of moderate-to-severe OSAS were assessed using multivariable logistic regression analyses. The discriminative performance of inflammatory markers was evaluated using receiver operating characteristic (ROC) curve analysis.
RESULTS: As OSAS severity increased, CRP, CAR, NLR, and SII levels showed a significant upward trend, whereas serum albumin levels decreased (all p <0.001). In multivariable analyses, CAR, NLR, and SII were independently associated with the presence of moderate-to-severe OSAS. ROC analysis demonstrated that CAR had the highest diagnostic accuracy for distinguishing moderate-to-severe OSAS.
DISCUSSION AND CONCLUSION: Increasing OSAS severity is associated with a marked elevation in systemic inflammatory burden. CAR may serve as a supportive inflammatory marker for identifying patients with moderate-to-severe OSAS.

Keywords: Sleep apnea, obstructive, C-reactive protein, albumins, inflammation