Association Between Nocturnal Oxygen Desaturation and the Severity of Obstructive Sleep Apnea: A Retrospective Study

Introduction Obstructive sleep apnea (OSA) is characterized by recurrent respiratory events and intermittent hypoxemia. This study examined the associations between the apnea-hypopnea index (AHI) and nocturnal oxygenation parameters. Materials and methods This retrospective single-center study included all consecutive eligible patients with OSA confirmed by nocturnal ventilatory polygraphy in the Department of Pulmonology at Mohammed VI University Hospital Center, Tangier, between 2023 and 2025. Recordings were obtained using the SOMNOtouch™ RESP device (SOMNOmedics GmbH, Randersacker, Germany) and analyzed with DOMINO light software (version 1.5.0), with automated analysis followed by systematic manual review and validation by an experienced pulmonologist. Respiratory events were scored according to the American Academy of Sleep Medicine (AASM) scoring criteria, version 2.5. Normality was assessed before inferential analyses. Pearson correlations were complemented by Spearman rank correlations, and Holm adjustment was applied across the four prespecified associations within each correlation family. Results The mean age was 57.06 ± 14.52 years, 55.8% were male, and the mean BMI was 33.26 ± 8.14 kg/m². The mean AHI was 24.69 ± 20.77 events/h. AHI was positively associated with oxygen desaturation index (ODI) (Pearson r = 0.893) and T90 (r = 0.699) and inversely associated with minimum nocturnal SpO₂ (r = -0.510) and mean nocturnal SpO₂ (r = -0.683); all Holm-adjusted p-values were <0.001. Spearman analyses were directionally concordant. Conclusion In this small retrospective single-center cohort, AHI was associated with several nocturnal oxygenation indices. These exploratory findings suggest related physiological patterns but do not establish independence, causality, prognostic value, or clinical utility beyond AHI. Larger prospective studies with multivariable and outcome-based analyses are warranted.