Abstract

Background: The relationship between obstructive sleep apnea (OSA) and coronary artery disease (CAD) remains controversial. Although observational studies have suggested that OSA is associated with an increased risk of coronary events, substantial confounding and neutral findings from treatment trials have raised uncertainty regarding which aspects of OSA are most strongly linked to CAD risk.

Aims: This study aimed to examine the association between nocturnal hypoxemia, assessed using the oxygen desaturation index (ODI), and incident CAD.

Study Design: Prospective cohort study.

Methods: Adults referred for evaluation of suspected OSA within the sleep apnea patients in Skaraborg study were prospectively followed for the occurrence of incident CAD. Associations between nocturnal hypoxemia, measured using the ODI, and incident CAD were investigated. Apnea-hypopnea index (AHI) categories were also analyzed for comparison. Multivariable Cox proportional hazards regression models were constructed, including models that evaluated AHI and ODI separately as well as simultaneously to determine their independent associations with CAD risk.

Results: The analytic cohort included 2,902 adults (1,012 women and 1,890 men) with a median follow-up duration of 8.7 years, during which 111 incident CAD events were identified. In fully adjusted Cox regression analyses, participants in the highest ODI category (≥ 30 events/h) had a significantly greater risk of incident CAD than those in the lowest category (hazard ratio, 1.99; 95% confidence interval, 1.08-3.65). In contrast, AHI categories were not independently associated with incident CAD. Moreover, when AHI and ODI were simultaneously included in the same model, ODI remained independently associated with incident CAD. In analyses restricted to adults with OSA, the association between ODI and CAD was attenuated and did not reach statistical significance, although the direction and magnitude of the association remained generally consistent with those observed in the primary analysis.

Conclusion: Among adults referred for OSA evaluation, nocturnal hypoxemia assessed using ODI, rather than event-based OSA severity, was associated with incident CAD. However, the absence of independent associations when both ODI and AHI were considered simultaneously suggests substantial overlap between these OSA severity metrics. These findings suggest that hypoxemia-related parameters may provide additional value for coronary risk stratification.