Increased 8-isoprostane and interleukin-6 in breath condensate of obstructive sleep apnea patients

Study objectives: Obstructive sleep apnea (OSA) is characterized by repeated episodes of upper airways obstruction during sleep that result in episodes of hypoxia. An increase of systemic biomarkers of inflammation and oxidative stress has been found in patients with OSA and obesity. Design: The aim of this study was to measure the levels of markers of inflammation (interleukin [IL]-6) and oxidative stress (8-isoprostane) in the exhaled breath condensate of OSA and obese patients. Patients and methods: Eighteen OSA patients (13 men; mean [+/- SEM] age, 44 +/- 7 years), 10 obese subjects (4 men; mean age, 39 +/- 8 years), and 15 healthy age-matched subjects (8 men; mean age, 42 +/- 4 years) were recruited. IL-6 and 8-isoprostane were measured in exhaled breath condensate by a specific enzyme immunoassay kit. Measurements and results: Higher concentrations of IL-6 were found in OSA patients (8.7 +/- 0.3 pg/mL) than in healthy control subjects (1.6 +/- 0.1 pg/mL; p < 0.0001). Obese subjects also had higher levels than healthy control subjects, but lower levels than OSA patients (2.1 +/- 0.2 pg/mL, p < 0.05 and p < 0.0001 respectively). Furthermore, 8-isoprostane levels were found to be higher in OSA patients (7.4 +/- 0.7 pg/mL) than in obese subjects (5 +/- 0.3 pg/mL; p = 0.4) and healthy subjects (4.5 +/- 0.5 pg/mL; p < 0.005). We found a positive correlation between these two markers and neck circumference and apnea/hypopnea index. Conclusions: These findings suggest that inflammation and oxidative stress are characteristic in the airways of OSA patients but not in obese subjects, and that their levels depend on the severity of the OSA. The measurement of IL-6 and 8-isoprostane levels may prove to be useful in screening and monitoring obese patients who have a high risk of developing OSA.