Babies' Nighttime Need for Shared Sleep
Why Infants and Parents Benefit from Co-sleeping
Mar 9, 2009
In cultures that define solitary infant sleeping arrangements as “normal,” the ability of babies to sleep through the night and to soothe themselves back to sleep without parental intervention is viewed as a desirable developmental milestone. Sleeping alone is popularly regarded as the healthiest and safest form of infant sleep by both psychologists and parents, who assume that this practice promotes physiological and social autonomy.
Cutting edge research is challenging the validity of these common assumptions. The research now points to the potential benefits to infants derived from sleeping in close proximity to their parents.
James J. McKenna, a professor with the University of Notre Dame Mother-Baby Behavioral Sleep Lab (Indiana, USA) has examined the safety of different sleep environments, as well as the physiological and psychological consequences of the different choices of sleeping arrangements parents make. He says: “Infants sleeping for long periods in social isolation from parents constitutes an extremely recent cultural experiment, the biological and psychological consequences of which have never been evaluated.” [1]
Human Babies Need to Sleep with their Mothers
Human mother-infant co-sleeping, according to James Mckenna, is biologically necessary. Born with only 25% of adult brain volume, the human baby is neurologically the most immature infant primate, the slowest developing and the most reliant on its mother for the longest period of time for physiological regulation and support. The composition of human milk necessitates short intervals between breastfeeds. Babies have tiny stomachs and human milk is very easily and quickly digested.
Babies’ Shorter Sleep Cycles
There are two main states of sleep: rapid eye movement sleep (REM), known as active sleep (when dreams occur), and non-REM (or quiet) sleep. During REM sleep, the eyes may be partially open and moving and breathing is irregular. Sleepers pass from wakefulness through four stages of gradually deepening non-REM sleep before moving gradually back through the stages of non-REM sleep. The movement to and from REM sleep and back happens in cycles throughout the night.
The younger the human being, the greater the percentage of REM sleep. The period of life when humans sleep the most and the brain is developing the most rapidly is also when they require the most REM sleep. It appears that the predominance of active sleep in infants has developmental benefits. Infants have shorter sleep cycles than adults, with nearly twice as much REM sleep. Babies don’t crash into non-REM sleep in the way adults do; they have an initial REM period and a transitional period before entering quiet sleep during which they awaken easily, and so may appear difficult to settle or awaken more easily in the night.
Parenting a Baby to Sleep
A baby can be parented to sleep through the initial REM state until he descends into deep sleep. Likewise, if a baby rouses during a subsequent period of REM sleep, he can be gentled through it until he is again in a deep sleep. Breastfeeding a baby is a wonderful way to gentle him to sleep and help him to settle in the night. Keeping mother and baby together limits disruption to the whole family's sleep.
It is unrealistic for parents to expect babies to sleep for long stretches. Attempting to train them to sleep usually leads to poor sleep for everyone as well as much frustration. The high percentage of REM sleep falls as babies mature. Nor can babies tell the time: they have little concept of day and night. As a baby grows, he will naturally adapt to the rhythm of life in his new environment and will require no prompting or training to do so.
[1] Trevathan, Wenda R. and McKenna J. “Evolutionary Environments of Human Birth and Infancy: Insights to Apply to Contemporary Life.” Children’s Environments 11(2): 13-36. 1994.
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