Sleep: A Window Into Autonomic Control in Children Born Preterm and Growth Restricted.

Study Objectives: Preterm birth and fetal growth restriction (FGR) are both associated with risk of hypertension in adulthood. Mechanisms leading to this pathology are unclear. In children aged 5-12 years, who were born preterm and FGR, we used sleep as a tool to assess autonomic control with assessment of cardiovascular structure and function.

Methods: Eighteen children born preterm and FGR, 15 children born preterm with appropriate birth weights for gestational age (AGA), and 20 AGA term-born children were studied. Children underwent overnight polysomnography with the addition of continuous noninvasive blood pressure (Finometer™). Spectral measures of heart rate variability (HRV), blood pressure variability (BPV), and baroreflex sensitivity were assessed and overnight urinary catecholamine levels measured. Echocardiographic studies (Vivid7, GE Healthcare) were performed and vascular compliance assessed (Miller Instruments™). Statistical comparisons were adjusted for age and body size.

Results: Compared to term children, preterm AGA children had increased high frequency HRV (p < .05) and BPV (p < .05) during sleep, reflecting increased parasympathetic activation and blood pressure changes related to respiration. Preterm FGR children had smaller left ventricular lengths, ascending aorta, and left ventricular outflow tract diameter (p < .05 for all) and vascular compliance was positively correlated with gestational age (r2 = 0.93, p < .05).

Conclusions: FGR combined with preterm birth did not alter autonomic control but altered heart structure in children. In contrast, preterm birth alone altered autonomic control but had no change in heart structure. These changes in children born preterm and FGR may contribute, in part, to increased risk of cardiovascular disease later in life but by different mechanisms.