Evaluation of 8-isoprostane as a biomarker of oxidative stress in children with obstructive sleep apnea syndrome

Background: Hypoxia-reoxigenation, characteristic of obstructive sleep apnea syndrome (OSAS), induces an increase of products of non-enzymatic free radical-catalyzed lipidic peroxidation, such as 8-isoprostane (8IsoP). Aim: To evaluate urinary 8IsoP values in children with OSAS. Methods: Thirty-eight children with OSAS (mean age:6.23±2.08yr, range:3.16-10.83yr M/F:26/12), underwent urinary collection at the morning after nocturnal polysomnography. 8Isop levels were measured with an enzyme immunoassay and corrected by urinary creatinine (uCR) levels. Results : According to the AHI (Apnoea/Hypopnea index, cut off>5 events/hours of sleep) obtained from polysomnography, we found 20 subjects (Group 1) with snoring/minimum OSAS (mean AHI:1.48±1.44 ev/hr; mean overnight oxygen saturation, SaO2:97.64±0.63%) and 18 subjects (Group 2) with moderate/severe OSAS (mean AHI:11.98±7.97 ev/hr; mean SaO2:96.51±1.98%). Compared to Group 1, urinary 8IsoP value was higher in Group 2 (1.10±0.66ng/mg uCR vs 0.76±0.36ng/mg uCR. p=0.046) and age was lower (5.45±1.69yr vs 6.93±2.18yr. p=0.033). We found a negative correlation between SaO2 and urinary 8IsoP (r=-0.42; p=0.009) and a positive correlation between AHI and urinary 8IsoP (r=0.32; 0.05