UCSF

Cardiac autonomic nervous system (ANS) measurements, respiratory sinus arrhythmia (RSA) and preejection period (PEP), are valid and reliable indicators of children’s sensitivity to stressors in their environment; however, there are few studies of RSA and PEP measures in children younger than three years of age and no known studies of children at 18-months of age. This was a cohort study of racially- and ethnically-diverse, low-income children studied from birth through five years of age. At 18-months (n = 134) and 36-months (n = 102) of age, children completed a developmentally challenging protocol that simultaneously assessed their RSA and PEP under resting and challenge conditions. Reactivity was calculated as the difference between challenge and resting measures. Four ANS profiles were created by dichotomizing reactivity, mean challenge minus rest, as positive or negative reactivity. This study revealed novel information about the distribution, stability, and continuity of RSA and PEP rest, challenge, and reactivity measures. There was a significantly different distribution of children among the ANS profiles from 18- to 36-months of age; although, there was some stability for the reciprocal PNS activation/SNS not activated profile. The relations between selected sociodemographic characteristics (biological sex, race, ethnicity, and federal poverty level (FPL)) and ANS profiles showed that their prevalence differed at 18- and 36-months of age. Logistic regression models revealed significant relationships between FPL and the coactivation and coinhibition profiles at 18-months and a borderline significant relationship between being Hispanic and the reciprocal SNS activation/PNS withdrawal profile at 36-months.