Obstructive sleep apnea and acute coronary syndrome often coexist and similar pathophysiological pathways, like endothelial dysfunction, sympathetic hyperactivity, intermittent hypoxia, and inflammation, all of which lead to poor cardiovascular outcomes. One of the main characteristics of OSA is nocturnal hypoxemia, which has long been thought to increase cardiovascular risk. However, new data points to a more nuanced connection between cardiovascular outcomes and hypoxemic load in individuals with coexisting OSA and ACS.
In this cohort, moderate to severe nocturnal hypoxemia may paradoxically be linked to a decreased likelihood of later cardiovascular events, according to recent data. Comprehending this seemingly paradoxical correlation is crucial from a therapeutic standpoint, as it could indicate adaptive ischemia preconditioning or modified physiological responses after ACS. Thus, this study determined if the degree of nocturnal hypoxemia in ACS patients with and without OSA was related to cardiovascular outcomes.
Pooled data from 2 prospective cohort studies including 2,810 ACS patients were analyzed retrospectively. The patients were divided into 3 tertiles as mild, moderate, and severe nocturnal hypoxemia, based on the percentage of time spent with arterial oxygen saturation below 90% (TSA90). One-year major adverse cardiovascular and cerebrovascular events (MACCE) were the main outcome. Multivariable analysis was conducted using Cox proportional hazards models.
Of the 2,810 patients, 1,408 had OSA and 1,402 did not. MACCE rates were lower in OSA patients with moderate and severe hypoxemia than those with mild hypoxemia (77.8 and 72.7 vs. 120.0 per 1,000 person-years, p=0.044). Severe hypoxemia was linked to a 50% reduced risk of MACCE (HR: 0.50, 95% CI: 0.29-0.87, p=0.015) and a 68% lower risk of non-fatal myocardial infarction (HR: 0.32, 95% CI: 0.12-0.86, p=0.023) following multivariable correction. Moderate hypoxemia was associated with 84% fewer cardiovascular deaths (HR: 0.16, 95% CI: 0.03-0.78, p=0.024) and 79% fewer all-cause deaths (HR: 0.21, 95% CI: 0.05-0.84, p=0.028).
U-shaped correlations between TSA90 and outcomes in OSA patients were found using restricted cubic spline analysis. No significant correlations were seen between the hypoxemia tertiles in non-OSA patients (all p>0.05). Overall, moderate to severe hypoxemia at night is associated with a decreased risk of cardiovascular events in individuals with acute coronary syndrome who also have obstructive sleep apnea.
Reference:
Zheng, W., Wang, X., Li, S.-Y., Fan, J.-Y., Ai, H., Zhang, J.-J., Drager, L. F., Sethi, R., Zhao, D., Lee, C.-H., & Nie, S.-P. (2025). Nocturnal hypoxemia is associated with lower cardiovascular events in patients with acute coronary syndrome and obstructive sleep apnea. Chest. https://doi.org/10.1016/j.chest.2025.11.052
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