Obstructive Sleep Apnea, oxidative stress, inflammation and endothelial dysfunction-An overview of predictive laboratory biomarkers.

OBJECTIVE Obstructive Sleep Apnea (OSA) represents an emerging public health concern with great impact on cardiovascular state. Oxidative stress (OS), inflammation and altered Nitric Oxide (NO) production are recognized as prominent mechanisms of many acute and chronic diseases and even of the normal aging process. They are investigated as major pathophysiological processes in OSA through the analysis and comparison of significative and validated biomarkers. MATERIALS AND METHODS The review is developed using as key terms "sleep apnea", "oxidative stress", "inflammation", and "endothelial dysfunction". Included studies must have followed the American Academy of Sleep Medicine guidelines according to the diagnosis and classification of OSA. Lipid, protein and DNA oxidation products, PCR, IL-6, IL-8, TNF-α, NO and nitrosative stress compounds, and endothelial functioning tests have been detected for their contribution in OSA along the last 3 decades. RESULTS Nocturnal intermittent hypoxia has emerged to be significantly associated to oxidative/nitrosative stress, increase in pro-inflammatory markers, imbalance in NO production, and endothelium impairment. Body Mass Index (BMI) contribution needs further clarifications. Continuous Positive Airway Pressure (CPAP) therapy has demonstrated beneficial effects on vascular function and pro-inflammatory milieu in OSA. CONCLUSIONS Oxidative stress and Inflammation significantly correlate with OSA; similarly, vascular functioning is impaired in accordance to unregulated levels of NO and derived compounds. Continuous Positive Airway Pressure markedly improves oxidative stress, inflammation and endothelial dysfunction in OSA.