Hirsch D, et al. - In children both with and without obstructive sleep apnea (OSA), researchers studied the links between biochemical markers and cardiac responses during exercise. They started with the premise that there would be a connection between serum markers of sympathetic nervous system activity and low-grade inflammation with cardiac responses to exercise in children with or without OSA. Morning levels of serum interleukin-6 (IL-6) were found to be elevated in children with OSA. Also, increased levels of interferon-gamma (IFN-γ) and interleukin-8 (IL-8) and decreased levels of metanephrine and normetanephrine were associated with poorer cardiac function during exercise.

Methods

• A total of 40 of 71 children with previously categorized responses to cardiopulmonary exercise testing were included.
• A multiplex bead-based assay was used to measure serum cytokine levels (interleukins IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, TNF-α and IFN-γ).
• Nephelometry was used to quantify serum amyloid A (SAA).
• By liquid chromatography, mass-spectroscopy, metanephrine/normetanephrine levels were measured.
• Children with and without OSA, and with and without obesity, were compared.
• Linear regression was used to determine the links between biomarkers and various cardiac parameters.

Results

• OSA was present in 23 of 40 children included in this study.
• Higher resting serum IL-6 levels were detected in those with OSA vs those without (median 3.22 pg/ml vs 2.31, p < 0.05).
• A negative correlation of IL-8 to heart rate (HR) response following exercise (p=0.03), and of IFN-γ with Stroke Volume Index (SVI) (p=0.03) was noted.
• A positive correlation of both metanephrine and normetanephrine levels with SVI (p=0.04, p=0.047; respectively) and QI (p=0.04, p=0.04; respectively) during exercise was noted when adjusting for OSA.