Myeloid-related protein 8/14 levels in children with obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is common in children and leads to multiple end-organ morbidities. Myeloid-related protein (MRP) 8/14 plays an important pathophysiological role in atherosclerosis, and plasma levels correlate with endothelial cell dysfunction. We hypothesised that MRP8/14 levels would be altered in children with OSA. 255 children (aged 7.6+/-1.5 yrs) were included after a sleep study and a morning blood sample. MRP8/14 and interleukin-6 plasma levels were assayed using ELISA and C-reactive protein by immunoturbidometry. Endothelial function was assessed as the hyperaemic response after occlusion of the brachial artery. Plasma log MRP8/14 levels showed apnoea/hypopnoea index (AHI) dose-dependent increases regardless of obesity. Moreover, log MRP8/14 levels correlated with log AHI (r = 0.340, p<0.001) after controlling for age and body mass index Z-score, and with endothelial function. Children with the highest MRP levels (>1.34 ug x mL(-1)) had 2.4- and 5.4-fold increased odds of mild OSA and moderate-to-severe OSA, respectively, after adjusting for confounding variables. Plasma MRP8/14 levels are associated with paediatric OSA and may reflect increased risk for cardiovascular morbidity. The short- and long-term consequences of elevated MRP8/14 on cardiovascular function in the context of paediatric OSA remain to be defined.