Cardiac vagal tone has been understood as the biological correlate of emotion regulation and can be divided into emotion regulation (tonic cardiac vagal tone (TCVT)) and the flexibility to adapt to changing conditions (phasic cardiac vagal tone (PCVT)). There is evidence that TCVT influences PCVT dynamics in adults and that stress exposure impacts on cardiac vagal tone in adults and older children. The aim of the study was to investigate the impact of TCVT on PCVT dynamics in preschoolers and to identify the influence of stress exposures on cardiac vagal tone.
Measures of heart rate variability including baseline (TCVT), during an age-adapted stress task (PCVT stress reactivity) and during recovery (PCVT recovery) were assessed in 222 children aged 2-6 years of the SPLASHY study. Further, parents were asked to complete questionnaires on early stress exposure (including pregnancy, birth and early life) and current stress exposure (including family stress and parenting).
Preschool children with high TCVT showed less PCVT reactivity (p < 0.001) and more increase of vagal tone (PCVT) during early recovery (p = 0.016). Further only child's low birth weight was a relevant stress exposure impacting on early and late PCVT recovery (p = 0.03/p = 0.005). None of the other early or late stress exposure conditions, nor the accumulation of stress exposures influenced TCVT or PCVT dynamics in these healthy preschoolers.
TCVT impacts on PCVT dynamics in a lab-based stress task in healthy preschool children and only low birth weight is related to more change during early and to less late PCVT recovery.