Rethinking "Healthy" Infant Sleep
James J. McKenna, PhD, Professor of Anthropology, Pomona College, Claremont, CA
from Breastfeeding Abstracts,
February 1993, Volume 12, Number 3.
Mother-infant co-sleeping
often accompanies nighttime breastfeeding. New research suggests that
co-sleeping affects infant physiology and patterns of arousal, raising
questions about currently accepted norms for "healthy" infant
sleep.
Judging from the infant's
biology and evolutionary history, proximity to parental sounds, smells,
gases, heat, and movement during the night is precisely what the human
infant's developing system "expects," since these stimuli
were reliably present throughout the evolution of the infant's sleep
physiology. The human infant is born with only 25 percent of its adult
brain volume, is the least neurologically mature primate at birth, develops
the most slowly, and while at birth is prepared to adapt, is not yet
adapted. In our enthusiasm to push for infant independence (a recent
cultural value), I sometimes think we forget that the infant's biology
cannot change quite so quickly as can cultural child care patterns.
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. Most Americans assume that solitary
sleep is "normal," the healthiest and safest form of infant
sleep. Psychologists as well as parents assume that this practice promotes
infantile physiological and social autonomy. Recent studies challenge
the validity of these assumptions and provide many reasons for postulating
potential benefits to infants sleeping in close proximity to their parents
- benefits which would not seem likely with solitary sleeping. Current
clinical models of the development of "normal" infant sleep
are based exclusively on studies of solitary sleeping infants. Since
infant-parent co-sleeping represents a species-wide pattern, and is
practiced by the vast majority of contemporary peoples, the accepted
clinical model of the "ontogeny" of infant sleep is probably
not accurate, but rather reflects only how infants sleep under solitary
conditions. I wonder whether our cultural preferences as to how we want
infants to sleep push some infants beyond their adaptive limits.
To explore this possibility
further, Dr. Sarah Mosko and I are studying the physiological effects
of mothers and infants sleeping apart and together (same bed) over consecutive
nights in a sleep lab. Our two pilot studies conducted at the University
of California, Irvine School of Medicine, showed that the sleep, breathing,
and arousal patterns of co-sleeping mothers and infants are entwined
in potentially important ways. Solitary sleeping infants have a very
different experience than social sleeping infants - although we do not
know yet what our data mean.
Funded by the National Institutes
of Child Health and Human Development, this research will help us to
evaluate the idea that infant-parent co-sleeping may change the physiological
status of the infant in ways that, theoretically, could help some (but
not all) SIDS-prone infants resist a SIDS event (McKenna 1986; McKenna
et al. 1991; McKenna et al., in press). One of the suspected deficits
involved in some SIDS deaths is the apparent inability of the infant
to arouse to reinitiate breathing during a prolonged breathing pause.
Our preliminary studies show that mothers induce small transient arousals
in their co-sleeping infants at times in their sleep when, had the infant
been sleeping alone, arousal might not have occurred. We have suggested
that perhaps co-sleeping provides the infant with practice in arousing.
Before we can draw any conclusions, more work is needed.
Regardless of what our own
research will reveal, there already exists enough scientific information
to justify rethinking the assumptions underlying current infant sleep
research, as well as pediatric recommendations as to where and how all
infants should sleep. Especially needed are new studies which begin
with the assumption that infant-parent co-sleeping is the normative
pattern for the human species-and that our own recent departure from
this universal pattern could have some negative effects on infants and
children. We need to determine if unrealistic parental expectations,
rather than infant pathology, play a role in creating parent-infant
sleep struggles - one of the most ubiquitous pediatric problems in the
country. It may well be that it is not in the biological best interest
of all infants to sleep through the night, in a solitary environment,
as early as we may wish, even though it is more convenient if they did
so.
Co-sleeping is often discussed
as if it were a discrete, all-or-nothing proposition (i.e., should baby
sleep with parents?). Many parents fail to realize that infants sleeping
in proximity alongside their bed, or with a caregiver in a rocking chair,
or next to a parent on a couch, in a different room other than a bedroom,
or in their caregiver's arms all constitute forms of infant co-sleeping.
I studied the location of infants and parents in their homes between
6:00 PM and 6:00 AM and found more infant-parent contact than parents
describe.
I prefer to conceptualize
infant sleep arrangements in terms of a continuum ranging from same-bed
contact to the point where infant-parent sensory exchanges are eliminated
altogether, as, for example, infants sleeping alone in a distant room
with the door closed. Nowadays, one-way monitors often broadcast infant
stirrings to parents in these situations, compensating for the loss
of sensory proximity.
I am amused by this baby
monitor phenomenon, primarily because we Americans seem to have gotten
it all backward. Rather than parents monitoring the infant, a great
number of developmental studies suggest that it should be the other
way around, with the infant processing parental stirrings (especially
breathing sounds and vocalizations). Infant sleep, heart rate, breathing,
and arousal levels are all affected by such stimuli, probably in adaptive
ways to facilitate development and to maximize adjustment to environmental
perturbations (Chisholm 1986). At the very least, monitors should be
broadcasting sound in both directions!
Given the human infant's
evolutionary past, where even brief separations from the parent could
mean certain death, we might want to question why infants protest sleep
isolation. They may be acting adaptively, rather than pathologically.
Perhaps these infant "signalers," as Tom Anders calls them,
have unique needs and require parental contact more than do some other
infants, who fail to protest. It's worth considering.
References
Chisholm, James. Navajo
Infancy: An Ethological Perspective. New York: Aldine de Gruyer,
1986.
Call, Justin. Commentary.Med
Anthropol 1986; 10(l): 56-57.
McKenna, James. An anthropological
perspective on the sudden infant death syndrome (SIDS): The role of
parental breathing cues and speech breathing adaptations. Med Anthropol
1986; 10(1) Special Issue.
MeKenna, J., S. Mosko, C.
Dungy, and J. McAnninch. Sleep and arousal patterns among co-sleeping
mother-infant pairs: Implications for SIDS. Am J Physical Anthropol
1991; 83:331-47.
McKenna, J., E. Thoman, A.
Sadeh, T. Anders et al. Infant-parent co-sleeping in evolutionary perspective:
Implications for infant development and the sudden infant death syndrome.
Sleep. In press.
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