Infant Weight-for-Length Gain Associated with Autonomic Nervous System Reactivity

BACKGROUND: Research suggests that children’s health and well-being are supported by core adaptive systems, including the autonomic nervous system (ANS). Despite evidence for the importance of adulthood ANS regulation in the development of disease, few studies have examined how early development may influence emerging ANS function. Therefore, we examined how infant adiposity gain during early infancy related to ANS regulation at 6-months. METHODS: Infant weight and length were abstracted from birth records and measured during the 6-month assessment in a low-income, racially/ethnically diverse sample (N = 60). WHO-standardized weight-for-length-gain change was calculated across the first 6 months of life. ANS reactivity was measured as the combined sympathetic (i.e., pre-ejection period) and parasympathetic (i.e., respiratory sinus arrhythmia) nervous system responses during the developmentally challenging Still Face Paradigm (SFP). ANS “classic reactivity” response was characterized by paired sympathetic activation and parasympathetic withdrawal. RESULTS: Lower weight-for-length gain in the first 6 months predicted classic reactivity during still face. However, greater weight-for-length gain predicted ‘classic reactivity’ during the reunion, when infants were expected to recover, suggesting autonomic dysregulation. CONCLUSION: These findings suggest an association between early life adiposity gain and the development of infant ANS regulation.