Oxygen desaturation index and apnea–hypopnea index in relation to incident heart failure: The sleep apnea patients in Skaraborg study

BACKGROUND: Obstructive sleep apnea (OSA) is associated with cardiovascular morbidity; however, it remains unclear whether the apnea-hypopnea index (AHI) or the severity of nocturnal hypoxemia, in terms of oxygen desaturation index (ODI), is more relevant for the development of heart failure (HF). METHODS: ) without prevalent HF at baseline and with available AHI and ODI data. Participants were followed for a median of 8.7 years (interquartile range 7.4-10.0). AHI and ODI were categorized as <5, 5-15, 15-30, and ≥30 events/hour. HF-free survival was analyzed using Kaplan-Meier methods and Cox proportional hazards models adjusted for demographic factors, cardiovascular comorbidities, and treatment with positive airway pressure or intraoral device. RESULTS: In total, 175 incident HF events occurred. Kaplan-Meier analyses showed lower HF-free survival with increasing AHI and ODI categories. After multivariable adjustment, ODI ≥30 events/hour was associated with a higher risk of incident HF (hazard ratio [HR] 1.78, 95% confidence interval [CI] 1.02-3.08). In contrast, no significant association was observed between AHI and incident HF (AHI ≥30 vs < 5: HR 1.27, 95% CI 0.92-1.75). OSA treatment was not significantly associated with HF risk (HR 0.91, 95% CI 0.66-1.25). CONCLUSIONS: In this large sleep clinic cohort with long-term follow-up, ODI ≥30 but not AHI ≥30 events/h was linked to the development of HF. These findings challenge the reliance on the AHI alone and highlight nocturnal hypoxemia as a central pathophysiological pathway connecting OSA to incident HF.