Agreement between apnea-hypopnea index and hypoxic burden for severity classification of obstructive sleep apnea

This study aimed to evaluate the agreement between apnea-hypopnea index (AHI)- and hypoxic burden (HB)-based obstructive sleep apnea (OSA) severity classifications. A retrospective single-center study of adults aged 18-79 years undergoing full-night in-laboratory polysomnography was conducted. OSA severity by AHI was categorized as normal (<5 events/hour), mild (5 to <15), moderate (15 to <30), or severe (≥30). HB severity was categorized as mild (<3.34), moderate (3.34 to 6.66), or severe (≥6.67). Agreement among patients with OSA (AHI ≥5) was assessed using Cohen's kappa. Ninety-five patients were included (mean age 58.4±18.3 years); 73 (76.8%) had OSA. Among these, HB severity exceeded AHI severity in 27.4%, was concordant in 61.6%, and was lower in 11.0%. Observed agreement was 30.1%, with slight concordance beyond chance (κ=0.168, p<0.001). Continuous AHI and HB were moderately correlated (r=0.663, p<0.001). Patients with HB greater than AHI severity demonstrated significantly lower nadir oxygen saturation (p=0.011). AHI- and HB-based OSA severity classifications demonstrate limited agreement. Incorporation of HB may provide a more physiologically informative assessment of OSA severity beyond event frequency alone.