Maturation of cardiovagal autonomic function from childhood to young adult age

Cardiovagal autonomic control declines with age in adult subjects, which is related in part to increasing stiffness of the barosensory vessel wall. It is not known, however, whether autonomic function changes with age in children. We studied 137 healthy subjects divided into 4 age groups: group 1, 7 to 14 years; group 2, 11 to 14 years; group 3, 15 to 18 years; and group 4, 19 to 22 years. Brachial artery pressure was measured by sphygmomanometry and continuous radial artery pressure and carotid artery pulse pressure (DeltaP) by applanation tonometry. The R-R interval was derived from the ECG. Autonomic function was assessed by spontaneous sequence and frequency-domain indices, which indicate the extent of coupling between fluctuations in heart rate and systolic pressure. Carotid artery diastolic diameter (DD) and pulsatile distension (DeltaD) were measured by echo wall tracking; carotid compliance coefficient (CC) was defined as DeltaD/DeltaP and distensibility coefficient as 2DeltaD/DD . DeltaP. From group 1 to group 3, spontaneous indices increased significantly (18.1+/-1.7 versus 33.3+/-4.0; 14.4+/-1.1 versus 25.5+/-22; 12.9+/-1.1 versus 20.8+/-2.0; and 6.4+/-0.6 versus 16.2+/-1.4 ms/mm Hg [mean+/-SEM] for Seq+, Seq-, LFalpha, and LF(gain), respectively), with no significant changes afterward. CC and DC were inversely proportional to age (r=-0.49 and -0.62, respectively, P