Caregivers' physiological responses during toddler vaccinations: associations with psychological and behavioral...

This study investigated biological, psychological, and behavioral aspects of caregivers' responses to toddlers' pain-related distress by measuring caregivers' high-frequency heart rate variability (HRV) responses during toddler vaccination pain and examining associations with caregivers' behavioral responses and psychological stress.

Participants included caregiver-toddler dyads (N = 194) from a longitudinal cohort-sequential study who were observed during toddlers' 12-, 18-, or 24-month routine vaccinations. Changes in caregiver HRV were analyzed using growth curve modeling. Conditional growth curve models examined associations between caregiver HRV and caregivers' concurrent behavior and psychological stress.

The unconditional growth curve model indicated a slight linear decrease in caregiver HRV (i.e., vagal withdrawal) across the 3 min post-needle (unstandardized B = -0.06, p = .049). In conditional growth curve models, higher levels of parenting stress were associated with less vagal withdrawal during the post-needle period (standardized B = 0.47, unstandardized B = 0.02, p = .003). Caregivers' behavioral responses (i.e., use of soothing and distress-promoting behaviors), state anxiety, and general anxiety symptomology were not significantly associated with HRV responses.

Caregiver parasympathetic nervous system activity levels changed minimally from baseline to post-needle and decreased slightly across the post-needle period. Caregivers' self-reported parenting stress was associated with their parasympathetic responses to the procedure. Findings support an improved understanding of the mechanisms underlying caregivers' responses to children's pain-related distress in a naturalistic setting.