Parent infant sleep synchrony: A test of two infant sleep locations

Abstract

This study contributes to the growing understanding of social sleep environments and their relationship to parent and infant behaviour and physiology by exploring the ways proximity and/or regularity of bed-sharing practice affect the physiology of parents and infants during triadic social sleep. The study explores the sleep physiology of 15 regularly and occasionally bed- sharing families, testing previous claims of shared sleep and arousals amongst breastfeeding mother infant dyads, and presents a new examination of the effects of proximity on mother infant physiology, and for the first time father infant physiology during bed-sharing compared to rooming in. Fifteen families considered low-risk for SIDS with breastfed infants less than 3 months of age were recruited from N. Tees region. Families either regularly slept their infant in a cot by the side of the parent's bed, or with the infant in the parent's bed. Circumstances under which co-sleeping was practised, and its frequency were assessed from sleep diaries, together with interview. Data were acquired by physiological monitoring via respiratory plethysmography bands, temperature probes (axillary and rectal), pulse oximeter probe (rubber type, not clip) and infra-red video capture over three nights (one adjustment night and two test nights) in the Durham University Sleep Lab. The two test night conditions were 1) infant sleeping in the parental bed 2) infant sleeping in a cot positioned next to the parental bed. Infant sleep/wake states were determined using cardio-respiratory video method. Sleep stages were subjectively assigned to 4 sleep state categories, awake (A WK), active asleep (REM), quiet sleep (QS) and indeterminate (IND), according to the characteristics predominant in any 1 minute epoch. Data from this study identified that mothers and infants experienced less time awake on bed-sharing nights and infants spent less time in Quiet sleep on the bed-sharing night; that regular bed-sharing infants experienced disruption to their sleep when separated from their mothers, but greater stability in their sleep physiology between by-the-bed sleeping and bed-sharing than occasional bed-sharing infants; that regularity of normal sleep condition only affected the shared sleep of regular bed-sharing mothers and infants on the bed-sharing night; and that sleep state synchrony and arousal synchrony were present amongst breastfeeding bed-sharing mothers and infants. Neither sleep condition nor regularity of normal bed-sharing practice made a discernable difference to paternal sleep state distribution and fathers did not demonstrate sleep state synchrony with their infants during social sleep. Paternal arousal behaviour was entirely unaffected by the location of the infant or their regular sleep location. Two noteworthy trends from the paternal data were that the absence of the father on the cot night affected both infant and mother sleep and that paternal habituation to sleeping practice was observed.