Fig 2: Simple linear regression graphs of the concentrations of OPG, YKL-40, and CT-1 in the serum. ROC curves of the concentrations of OPG, YKL-40, and CT-1 in the serum. The results of Spearman correlation analysis are expressed as r values and the level of statistical significance (p). The values of r with p < 0.05 were considered statistically significant. The coefficient of determination is expressed as R2. The simple linear regression models for serum OPG, YKL-40, and CT-1 use AHI as a single explanatory variable. The Receiver Operator Characteristic curve analysis is calculated for all subjects in classifying for OSA and non-OSA groups. Abbreviations: OSA, Obstructive Sleep Apnea; OPG, Osteoprotegerin; YKL-40, Chitinase-3 like protein-1; CT-1, Cardiotrophin-1; AHI, Apnea–Hypopnea Index; ROC, Receiver Operator Characteristic; AUC, Area Under the Curve.

Fig 3: ROC curves of the combined concentrations of OPG, YKL-40, and CT-1 in the serum and plasma. Receiver Operator Characteristic curve analysis is calculated for all subjects in classifying for OSA and non-OSA groups. Abbreviations: OSA, Obstructive Sleep Apnea; OPG, Osteoprotegerin; YKL-40, Chitinase-3 like protein-1; CT-1, Cardiotrophin-1; AHI, Apnea–Hypopnea Index; ROC, Receiver Operator Characteristic; AUC, Area Under the Curve.