Obstructive sleep apnea, inflammation, and cardiopulmonary disease

Obstructive sleep apnea (OSA) occurs commonly in the U.S. population and is seen in both obese as well as non-obese individuals. OSA is a disease characterized by periodic upper airway collapse during sleep, which then results in either apnea, hypopnea, or both. The disorder leads to a variety of medical complications. Neuropsychiatric complications include daytime somnolence, cognitive dysfunction, and depression. Increased incidence of motor vehicle accidents has been documented in these patients and probably reflects disordered reflex mechanisms or excessive somnolence. More importantly, vascular disorders such as hypertension, stroke, congestive cardiac failure, arrhythmias, and atherosclerosis occur frequently in these patients. The lungs may be affected by pulmonary hypertension and worsening of asthma. Recent data from several laboratories demonstrate that obstructive sleep apnea is characterized by an inflammatory response. Cytokines are elaborated during the hypoxemic episodes leading to inflammatory responses as marked clinically by elevated C-reactive protein (CRP). As elevated CRP levels are considered markers of the acute phase response and characterize progression of vascular injury in coronary artery disease, it is likely that obstructive sleep apnea could lead to worsening of vasculopathy. Moreover, as inflammatory mechanisms regulate bronchial asthma, it is also likely that cytokines and superoxide radicals generated during hypoxemic episodes could exacerbate reactive airway disease. Patients with Cough, Obstructive sleep apnea, Rhinosinusitis, and Esophageal reflux clustered together can be categorized by the acronym, "CORE", syndrome. The purpose of this manuscript is to review the inflammatory responses that occur in patients with obstructive sleep apnea and relate them to the occurrence of cardiopulmonary disease.