Plasma β-Endorphin and Neuropeptide Y as Candidate Biomarkers for Predicting Obstructive Sleep Apnea Syndrome: A Preliminary Study.

Background and Objective: Given the involvement of neuropeptides in the pathophysiology of obstructive sleep apnea syndrome (OSAS), this study investigated the associations between plasma levels of β-endorphin (β-EP) and neuropeptide Y (NPY) and OSAS severity and evaluated their potential as predictive biomarkers. Methods: A total of 48 snoring patients undergoing polysomnography (PSG) were categorized into non-OSAS, mild, moderate, and severe OSAS groups (n = 12 per group) based on the apnea-hypopnea index (AHI). Plasma levels of β-EP and NPY were measured using ELISA. Statistical analyses included one-way ANOVA, Spearman's correlation, and receiver operating characteristic (ROC) curve analysis to assess predictive performance. Results: Plasma β-EP levels exhibited significant elevation in moderate (p=0.003) and severe OSAS groups (p=0.032) compared to the non-OSAS group. Notably, NPY levels demonstrated marked differences across all OSAS severity groups (p < 0.01), with significantly higher concentrations observed in mild, moderate, and severe OSAS patients versus non-OSAS controls (p < 0.01). A progressive increase in NPY levels was observed with advancing OSAS severity, accompanied by statistically significant intergroup differences (p < 0.01). Correlation analyses revealed strong positive associations between NPY levels and both BMI (p < 0.0001) and AHI (p < 0.0001). In contrast, β-EP correlated positively with AHI (p < 0.0001) but not with BMI (p=0.0931). ROC curve analysis identified β-EP (cutoff: 9.405 ng/L) as a moderate predictor of OSAS (AUC = 0.7986, p < 0.01; sensitivity: 72.22%, specificity: 83.33%). Strikingly, NPY (cutoff: 19.29 ng/L) exhibited perfect discriminative capacity (AUC = 1, p < 0.0001; sensitivity: 97.22%, specificity: 100%). Conclusions: Plasma β-EP and NPY levels are associated with OSAS severity and may serve as potential biomarkers. However, further validation in larger cohorts is needed to confirm their clinical utility.