Obstructive sleep apnea: A unifying link between cardiovascular and renal disease

Obstructive sleep apnea (OSA) is a highly common, yet often under recognized, chronic sleep disorder characterized by transient, repetitive partial or complete disruptions of breathing due to upper airway obstruction during sleep. It is usually associated with disturbed sleep pattern, snoring, daytime fatigue, and poor concentration. The full metabolic derangement caused by OSA is unknown, but there is a growing body of evidence to suggest that sleep apnea is a chronic inflammatory systemic disease suggesting interplay between chronic disorders such as coronary artery disease and chronic kidney disease (CKD). OSA can result in direct kidney injury through hypoxia. It can also accelerate the deterioration of kidney function in patients with CKD indirectly by increasing systemic blood pressure, producing inflammatory cytokines, inducing endothelial dysfunction and increasing sympathetic activation. Better understanding of etiology and mechanisms is crucial to early diagnosis and aggressive management, as OSA has been associated with worse clinical outcomes and may be an independent predictor of all-cause mortality, hypertension, diabetes, left ventricular dysfunction, atrial fibrillation, stroke, and more recently, sudden cardiac death. The aim of this chapter is to describe and help readers better understand sleep apnea as a systemic disease and elucidate possible pathophysiological interactions between OSA and CKD in predisposing individuals to adverse cardiovascular events.