Abstract :
Keywords Respiratory sinus arrhythmia; Parasympathetic nervous system; Physiological regulation; Breastfeeding; Mother-infant interaction Highlights * Vagal regulation, indexed by RSA, supports self-regulation and social engagement * The longer breastfeeding duration is associated with lower infant RSA throughout the still-face paradigm * The longer breastfeeding duration is associated with higher overall RSA levels in mothers throughout the still-face paradigm * Continuation in breastfeeding contributes to infant adaptive vagal regulation during an interaction Abstract Background Vagal regulation within the parasympathetic nervous system supports self-regulation and social engagement. Research has suggested that early feeding practices may influence mother-infant vagal functioning. Aim We aimed to examine the association between breastfeeding duration and mother-infant vagal regulation during an interaction. We hypothesized that breastfeeding duration would be positively associated with adaptive vagal regulation in infants and mothers. Method 204 mother-infant dyads (infant mean age 6 months) completed the face-to-face still-face (FFSF) task. During the task, vagal regulation indexed by respiratory sinus arrhythmia (RSA, a component of heart rate variability) was calculated through continuously recorded electrocardiogram signals. Breastfeeding duration and demographic information were reported by mothers. Linear mixed models were adopted to estimate the associations between breastfeeding duration and repeated measures of RSA in infants and mothers throughout the FFSF. Results Infants breastfed for a longer duration demonstrated lower RSA throughout the FFSF (B = -0.06, 95 % CI: -0.09 to -0.03), suggesting active physiological mobilization to engage in interaction and regulate distress. Mothers with longer breastfeeding duration displayed higher baseline RSA and higher overall RSA levels (higher vagal control) during the FFSF (B = 0.06, 95 % CI: 0.02 to 0.09), indicating a calmer and regulated state. Conclusion Longer breastfeeding duration was associated with more adaptive mother-infant vagal regulation during the interaction, indicating a positive dose-response association. This finding reveals breastfeeding practice as a factor contributing to infant effective vagal regulation and further supports WHO recommendation on exclusive breastfeeding for the first 6 months and continuing breastfeeding to 24 months and beyond. Abbreviations RSA, respiratory sinus arrhythmia; FFSF, face-to-face still-face Author Affiliation: (a) School of Psychological and Cognitive Sciences and Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing, China (b) United Nations Children's Fund (UNICEF) Office for China, Beijing, China * Correspondence to: Li Wang, School of Psychological and Cognitive Sciences and Beijing Key Laboratory of Behavior and Mental Health, Peking University, No. 5 Yiheyuan Road, Haidian District, Beijing, China, 100871. Article History: Received 29 September 2021; Revised 24 June 2022; Accepted 24 June 2022 Byline: Qili Lan (a), Hongxia Li (a), Li Wang [liwang@pku.edu.cn] (a,*), Suying Chang [schang@unicef.org] (b,**)