Background: Previous studies present contradictory data concerning obstructive sleep apnoea syndrome (OSAS), lipid oxidation and nitric oxide (NO) bioavailability.
Objectives: This study was aimed: (1) to compare the concentration of 8-isoprostane and total nitrate and nitrite (NOx) in plasma of middle aged males with OSAS and no other known comorbidity and healthy controls of the same age, gender and body mass index; and (2) to test the hypothesis that nasal continuous positive airway pressure (CPAP) therapy attenuates oxidative stress and nitrate deficiency.
Methods: In this prospective randomized, placebo-controlled, double-blind, cross-over study, 31 consecutive newly diagnosed middle-aged OSAS men and 15 healthy control subjects were selected. OSAS patients were randomized to sham CPAP and effective CPAP application for 12 weeks. Blood pressure, urinary catecholamine levels and 8-isoprostane concentrations and NOx in plasma were obtained before and after both treatment modalities.
Results: OSAS patients had significantly higher 8-isoprostane concentration (median (interquartile range (IQR)) 42.5 (29.2-78.2) vs. 20.0 (12.5-52.5) pg/ml, p=0.041, Mann-Whitney test) and lower NOx (264 (165-650) vs. 590 (251-1465) µmol/l, p=0.022) than healthy subjects. Body mass index, blood pressure or urinary catecholamines were unchanged by CPAP therapy, but 8-isoprostane concentration decreased (38.5 (24.2-58.7) pg/ml at baseline and 22.5 (16.2-35.3) pg/ml on CPAP, p=0.0001), and NOx increased (280 (177-707) vs. 1373 (981-1517) µmol/l, p=0.0001) after it.
Conclusions: OSAS is associated with an increase in oxidative stress and a decrease in NOx that is normalized by CPAP therapy.