Abstract

Purpose: The severity of obstructive sleep apnea (OSA) is traditionally assessed using the Apnea–Hypopnea Index (AHI), as recommended by the American Academy of Sleep Medicine (AASM). However, the Spanish Society of Pulmonology and Thoracic Surgery (SEPAR) has proposed a multidimensional classification incorporating additional clinical factors. This study aimed to compare OSA severity distribution between the AASM and SEPAR classification systems in an adult population. Methods: A retrospective cross-sectional study was conducted. OSA severity was classified using AHI-based criteria (AASM) and SEPAR, which integrates total recording time with oxyhemoglobin saturation below 90% (T90%), body mass index (BMI), Epworth Sleepiness Scale (ESS), and cardiovascular history (CV). Transition analysis was performed to evaluate reclassification patterns, and logistic regression models were used to identify factors associated with higher severity categorization under SEPAR. Results: The SEPAR classification resulted in a higher proportion of cases categorized as severe compared to AASM (50.9% vs. 72.8%, p < 0.001). T90% and BMI were the primary contributors to this reclassification, with 24% of patients initially classified as moderate under AASM criteria reclassified as severe using SEPAR. Conclusion: AHI-based classification alone may underestimate OSA severity, particularly in individuals with significant nocturnal hypoxemia or obesity. Integrating multidimensional criteria identifies a more considerable proportion of severe cases, with potential implications for treatment prioritization and risk stratification. These findings support the need for broader evaluation strategies in clinical practice. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.