Ascending aortic blood flow velocity is increased in children with primary snoring/mild sleep-disordered breathing and associated with an increase in CD8⁺T cells expressing TNFα and IFNγ

Abstract

Sleep-disordered breathing (SDB) is associated with cardiovascular disease and systemic inflammation in adults but this remains to be explored in children, especially in children with the most common form of SDB, i.e. primary snoring/mild SDB. This pilot study investigated the relationship between the cardiovascular function and inflammation in children with mild SDB. Nineteen participants aged 5-14 years underwent overnight polysomnography, cardiac magnetic resonance imaging (aortic blood flow velocity and left and right ventricular systolic function) and assessment for inflammatory markers (intracellular cytokine analysis of T cells by flow cytometry). Parents also completed the Sleep Disturbances Scale for Children (SDSC). Children with mild SDB exhibited increased ascending aortic peak systolic velocity compared to controls (SDB 119.95 m/s vs. control 101.49 m/s, p < 0.05). No significant group differences were observed for left and right ventricular ejection fraction or mean aortic blood flow velocity from either the ascending aorta or pulmonary artery. Children with mild SDB had increased inflammatory markers as demonstrated by elevated T cell interferon gamma (IFNγ) (SDB 52 ± 4% vs. control 25 ± 3% positive cells, p < 0.005) and tumour necrosis factor alpha (TNFα) (SDB 39 ± 4% vs. control 20 ± 2% positive cells, p < 0.005) expression from CD8(+) cells. A strong positive correlation was observed between ascending aorta peak blood flow velocity and both TNFα and IFNγ (TNFα, r = 0.54, p < 0.03; IFNγ, r = 0.63, p < 0.005, respectively). Polysomnography revealed that oxygen saturation (SaO2) nadir was significantly lower in children with mild SDB compared to controls (SDB 92.3 ± 2.7% vs. control 94.4 ± 1.6%, p < 0.05). A lower SaO2 nadir was associated with an increased ascending aorta peak systolic velocity (r = - 0.48, p < 0.05). As well, both a lower SaO2 nadir and an increased ascending aorta peak systolic velocity were associated with higher SDSC Sleep-Disordered Breathing and Disorder of Initiating and Maintaining Sleep subscale scores but not the polysomnographic-derived Obstructive Apnea-Hypopnea Index. The finding of elevated ascending aortic peak systolic blood flow velocity and its association with increased inflammatory markers suggests that the profile of cardiovascular changes noted in adult SDB may also occur in children with mild SDB.