Rhythmic organization of heart rate in breast‐fed and bottle‐fed newborn infants

Abstract

Heart rates and behavioural states of 14 breast-fed and 14 bottlefed newborn infants were assessed every 30 seconds for 2 continuous hours. The 240 observations of heart rate were treated as time-series data and spectrum-analysed for behavioural rhythmicities. Of the 28 infants, 25 showed reliable cycles in heart rate; 22 of the 25 infants showed a dominant frequency with a 30-60 min periodicity, one that approximates the basic-rest activity cycle (BRAC). In addition to this basic cycle, additional higher frequency cycles in long-term heart rate variability were evident in the spectra of many infants. Breast-fed newborns had greater numbers of reliable cycles in heart rate than bottle-fed newborns. Further, breast-fed newborns had lower overall mean heart rates and lower mean heart rates in Quiet and Active Sleep states than bottle-fed newborns. Bottle-fed newborns were observed more often in Quiet Sleep than breast-fed newborns. Without knowledge of the specific mechanisms causing these behavioural differences, the results of this study suggest that the context in which breast-feeding occurs results in a more complex and energy-efficient pattern of behavioural organization than the context of bottle-feeding.

Role of essential fatty acids in the function of the developing nervous system

“…There is a progressive dominance of the sympathetic tone in AS, also called rapid eye movement (REM) sleep, and a predominance of the parasympathetic vagal tone in QS or non-REM sleep. Our preliminary findings (Uauy, R., and Peirano, P., unpublished observations) support published reports of a higher HRV during AS and QS in HM-fed infants, indicating a more mature pattern of CNS development (58,59). The effect is observed in all frequency components but is more marked in the high-frequency component, suggesting a higher parasympathetic vagal tone in the HM-fed group.…”

“…There are indications that breast-fed neonates even at the age of 2 d postpartum are better organized, physiologically, than are bottle-fed neonates (58,59). They exhibit a more organized HRV pattern and a slower heart rate in both AS and QS.…”

Mechanisms for Nutrient Effects on Brain Development and Cognition

“…Nocturnal sleep-wake states organization at 4 months of age show that breast-fed infants spend a higher percentage of time in quiet sleep (QS) and a lower percentage of time in AS as compared to formula-fed infants [87]. Furthermore, heart rate values were lower in all sleep-wake states in breast-fed infants [88]. Even though total energy expenditure during AS and QS did not differ between feeding groups, the different organization of sleep states throughout the night might account for differences in energy expenditure between feeding groups [86,87].…”

“…Breast-fed neonates, even at the age of 2 days' postpartum, are better organized, physiologically, than bottle-fed neonates [88,89]. They exhibit slower overall mean heart rate in both AS and QS.…”

Antenatal origins of individual differences in heart rate

“…Five infants could not be recorded due to prolonged fussiness or high motor activity, four were successfully recorded during a period of either drowsiness or quiet wakefulness, and the remainder during predominantly active sleep. Most of the subjects were breast-fed (n 35), but because feeding method in infancy affects cardiac patterns (Butte, Smith, & Garza, 1991;DiPietro, Larson, & Porges, 1987;Zeskind, Marshall, & Goff, 1992), analyses were conducted on both the full sample and without the six exclusively formulafed infants. At 1 year, 35 (67%) subjects returned for follow-up (M 53.4 weeks; SD 1.0); the average length of ECG recording was 7 min (SD 1.6).…”