Hypoxemia burden and atherogenic indices in OSAS: changes after CPAP therapy

Objective: To evaluate the association between nocturnal hypoxemia burden-expressed as the percentage of total sleep time spent below 90% oxygen saturation (%T90/TST)-and atherogenic indices, including the atherogenic index of plasma (AIP), Castelli risk index I (CRI-I), and Castelli risk index II (CRI-II), in obstructive sleep apnea syndrome (OSAS); and to assess pre-post changes after adherent continuous positive airway pressure (CPAP) therapy. Methods: Single-centre retrospective-prospective cohort of adults with moderate-severe OSAS. Hypoxemia burden was quantified as the percentage of total sleep time with peripheral oxygen saturation (SpO₂) < 90% (%T90/TST) and grouped as Low (≤5%), Mild (>5-≤10%), Moderate (>10-≤25%), and Severe (>25%). The lipid panel-total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG)-and atherogenic indices (AIP, CRI-I, CRI-II) were compared across %T90 groups and within patients before and after ≥3 months of adherent CPAP (device-verified ≥4 h/night on ≥70% of nights). Results: = 0.570). Primary endpoints (CRI-I/II, AIP) remained significant after Bonferroni correction. Conclusion: In OSAS, greater hypoxemia burden (%T90/TST) is linked to a more atherogenic lipid profile, and adherent CPAP is associated with a meaningful reduction in atherogenic load (AIP, CRI-I/II). These findings indicate that nocturnal hypoxaemia, captured using index-based measurements (AIP, Castelli I/II) as well as traditional lipids, is associated with a general reduction in atherogenic risk.