Obstructive Sleep Apnea in Adults and the Autonomic Nervous System

Obstructive sleep apnea (OSA) is characterized by episodic collapse of the upper airway during sleep, resulting in periodic reductions or pauses in ventilation, resulting in hypoxia, hypercapnia, or arousals from sleep. OSA is very frequent in the general population with an estimated prevalence of 3% among women and 10% among men aged 30–49 years and 9% among women and 17% among men aged 50–70 years. OSA is associated with increased risk of hypertension, stroke, coronary artery disease, heart failure, sinus bradycardia, atrioventricular block, ventricular tachycardia, and sudden death. The increase in cardiovascular morbidity and mortality is mediated by sustained increases in sympathetic efferent and cardiovagal activity caused by the repetitive hypoxias and apneas. The most effective therapy to treat moderate and severe OSA is positive airway pressure (CPAP). Although there is consistent evidence that CPAP therapy reduces sympathetic efferent activity and improves cardioascular autonomic tone in patients with OSA, the effects of CPAP therapy on hypertension, cardiovascular events, and survival remain uncertain, and more controlled trials are required. The effect of CPAP on cardiac arrhythmias is also unknown. Novel therapeutic approaches are redefining the relationship between OSA and autonomic dysfunction and treatment with CPAP may be a potential therapeutic option for the treatment of supine hypertension in patients with autonomic failure, regardless of the presence of OSA.