Biochemical markers of cardiac dysfunction in children with obstructive sleep apnoea (OSA).

OBJECTIVES: We explored relationships between biochemical markers and cardiac responses of children with and without obstructive sleep apnoea (OSA) during exercise. We hypothesised that serum markers of sympathetic nervous system activity and low-grade inflammation would correlate with cardiac responses to exercise in children with or without OSA.

METHODOLOGY: The study included 40 of 71 children with previously characterised responses to cardiopulmonary exercise testing. Measures included serum cytokine levels using a multiplex bead-based assay (interleukins IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, TNF-α and IFN-γ). Serum amyloid A (SAA) was quantified by nephelometry, and metanephrine/normetanephrine levels were measured by liquid chromatography, mass-spectroscopy. Comparisons were made between children with and without OSA, and with and without obesity. Relationships between biomarkers and various cardiac parameters were explored by linear regression.

RESULTS: Amongst the 40 children in this study, OSA was present in 23. Compared to the 17 children without OSA, those with OSA had higher resting serum IL-6 levels compared to those without (median 3.22 pg/ml vs. 2.31, p < 0.05). Regarding correlations with cardiac function after adjusting for OSA, IL-8 negatively correlated to heart rate (HR) response following exercise (p = 0.03) and IFN-γ negatively correlated with Stroke Volume Index (SVI) (p = 0.03). Both metanephrine and normetanephrine levels positively correlated with SVI (p = 0.04, p = 0.047; respectively) and QI (p = 0.04, p = 0.04; respectively) during exercise when adjusting for OSA.

CONCLUSIONS: Children with OSA have raised morning levels of serum IL-6. Separately, higher levels of IFN-γ and IL-8 and lower levels of metanephrine and normetanephrine related to poorer cardiac function during exercise.