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

We included 3590 participants from the Sleep Apnea Patients in Skaraborg Study (mean age 54.6 ± 12.8 years, 66% men, mean body mass index 29.6 ± 5.4 kg/m2) 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.