Obstructive sleep apnea and coronary artery disease: An unholy nexus or a holy alliance?

Coronary artery disease (CAD) is a significant cause of morbidity and mortality globally, and hypertension, dyslipidemia, diabetes mellitus, and smoking are major cardiovascular (CV) risk factors. Obstructive sleep apnea (OSA) and CAD share an exciting relationship, and recently, OSA has emerged as a non-traditional CV risk factor. OSA is characterized by episodic sleep state-dependent collapse of the upper airway, resulting in periodic reductions or cessations in ventilation, with consequent hypoxia, hypercapnia, or arousals from sleep. The oxidative stress and vascular inflammation resulting from the nocturnal hypoxia followed by reoxygenation cycles predispose the patients to the development of atherosclerotic cardiovascular disease (CVD). Untreated OSA is associated with long-term health consequences, including CVD, metabolic disorders, cognitive impairment, and depression. Paradoxically, some recent studies have reported that patients with OSA may suffer less severe CAD due to the development of collateral circulation due to repetitive hypoxia experienced due to OSA.