James J. McKenna

Experimental studies of infant-parent co-sleeping: mutual physiological and behavioral influences and their relevance to SIDS (sudden infant death syndrome)

We hypothesize that maternal sensory exchanges, likely involving a combination of heat, sound, gas, smells, movement, and touch, induce important physiological changes, especially in the healthy infants arousal patterns, body temperature, and sleep architecture as defined by standard physiological measures. We summarize the results of two preliminary physiological studies, and some early data from a third, in which mothers and infants are monitored using standard polysomnographic techniques as they sleep in the same bed, and then in adjacent rooms. Our data suggest that infant-parent co-sleeping alters the infants sleep experience as, for example, the characteristics of arousals, the frequency and duration of nursing, infant sleep position and the number of maternal inspections. For example, while sleeping in the same bed, mothers nurse their infants three times more frequently than they do while their infants sleep in an adjacent room. These preliminary data demonstrate significant differences between routine co-sleeping and solitary sleeping environments. This work underscores the importance of studying infant sleep as it unfolds in the co-sleeping environment, the environment within which it evolved over at least 5 million years of human evolution. Should our preliminary findings be confirmed in future studies they will provide a beginning point for considering additional, possibly unconventional ways of helping to reduce SIDS risks.

Evolution and the sudden infant death syndrome (SIDS)

This paper extends the evolutionary and developmental research model for SIDS presented in previous articles (McKenna 1990a, 1990b). Data from variety of fields were used to show why we should expect human infants to be physiologically responsive in a beneficial way to parental contact, one form of which is parent-infant co-sleeping. It was suggested that on-going sensory exchanges (touch, movement, smell, temperature, etc.) between co-sleeping parent-infant pairs might diminish the chances of an infantile cardiac-respiratory crisis (such as those suspected to occur in some SIDS cases).In this article we review recent epidemiological data and sleep research findings on SIDS to show how they relate to evolutionary and cross-cultural perspectives. Results of a preliminary study of the co-sleeping behavior of mother-infant pairs indicate that, with respect to sleep, arousal, and respiratory patterns, co-sleeping mother-infant pairs affect each other in potentially important ways. We suggest specifically that co-sleeping may shorten periods of consolidated sleep among young infants by causing them to arouse more frequently. Moreover, we suggest that partner-induced arousals might help the infant to confront sleep crises more competently. In the long run, these arousals might prevent the premature emergence of prolonged (adultlike) sleep bouts from which some infants have difficulty arousing—especially during a breathing pause or apnea.

Sleep and arousal, synchrony and independence, among mothers and infants sleeping apart and together (same bed): an experiment in evolutionary medicine

Although solitary sleeping in infancy is a very recent custom, limited to Western industrialized societies, and most contemporary people practice parent‐infant co‐sleeping, virtually all laboratory research on sleep in human infants assumes that solitary infant sleep is the normal and desirable environment. We have used evolutionary and developmental data to challenge this view. We suggest that co‐sleeping provides a sensory‐rich environment which is the more appropriate environment in which to study infant sleep. In addition, two preliminary, in‐laboratory, polygraphic investigations of mother‐infant co‐sleeping are reported in normal infants, within the peak age range for sudden infant death syndrome (SIDS). Five mother‐infant pairs co‐slept one night in the first study; in the second, three additional pairs slept separately for two nights and co‐slept the third consecutive night. The results suggest that co‐sleeping is associated with enhanced infant arousals and striking temporal overlap (synchronicity) in infant and maternal arousals, and that, possibly as a result, co‐sleeping mothers and infants spend more time in the same sleep stage or awake condition. The implications of the hypothesis and preliminary results for research on the normal development of infant sleep and on SIDS are discussed.

Cosleeping (bedsharing) among infants and toddlers.

CASEJaquette, a 4-month-old African-American infant, is brought to the pediatrician for a health supervision visit. She was born full term after a healthy gestation, labor, and delivery. She nurses vigorously, developmental milestones are normal, and her physical examination reveals an emotionally r

Parent-infant cosleeping: The appropriate context for the study of infant sleep and implications for sudden infant death syndrome (SIDS) research

Nearly all laboratory research on human infant sleep assumes that solitary sleeping is the normal and desirable environment. Yet solitary sleeping in infancy is a very recent custom limited to Western industrialized societies, and most of the worlds peoples still practice parent-infant cosleeping. A hypothesis is presented that cosleeping provides a sensory-rich environment which is the more appropriate environment in which to study normal infant sleep. In addition, two preliminary, in-laboratory, polygraphic investigations of mother-infant cosleeping are reported in normal infants within the peak age range for sudden infant death syndrome (SIDS). Five mother-infant pairs coslept for 1 night in the first study; in the second, three additional pairs slept separately for 2 nights and coslept the third consecutive night. The results suggest that cosleeping is associated with enhanced infant arousals and striking temporal overlap in infant and maternal arousals. Infant sleep also showed subtle alterations with cosleeping, as manifested in increased overlap with corresponding maternal sleep stages and decreased amount of Stage 3–4. These are the first in-laboratory investigations of parent-infant cosleeping. The implications of the hypothesis and preliminary results for research on the normal development of infant sleep and on SIDS are discussed.

Evolution and sudden infant death syndrome (SIDS) : Part I: Infant responsivity to parental contact.

This paper and its subsequent parts (Part II and Part III) build on an earlier publication (McKenna 1986). They suggest that important clinical data on the relationship between infantile constitutional deficits and microenvironmental factors relevant to SIDS can be acquired by examining the physiological regulatory effects (well documented among nonhuman primates) that parents assert on their infants when they sleep together.I attempt to show why access to parental sensory cues (movement, touch, smell, sound) that induce arousals in infants while they sleep could possibly help one of many different subclasses of infants either to override certain kinds of sleep-induced breathing control errors suspected to be involved in SIDS or to avoid them altogether. I do not suggest that solitary nocturnal sleep “causes” SIDS, that all parents should sleep with their infants, or that traditional SIDS research strategies should be abandoned. However, using evolutionary data, I do suggest that an adaptive fit exists between parent-infant sleep contact and the natural physiological vulnerabilities of the neurologically immature human infant, whose breathing system is more complex than that of other mammals owing to its speech-breathing abilities. This “fit” is best understood, it is argued, in terms of the 4–5 million years of human evolution in which parent-infant contact was almost certainly continuous during at least the first year of an infant’s life. Thus, to dismiss the idea that solitary sleep has no physiological consequences for infants does not accord with scientific facts.

Susceptibility of Walnut and Hickory Species to Geosmithia morbida

Thousand cankers disease (TCD) of walnut is a result of feeding in the phloem by the walnut twig beetle (WTB), Pityophthorus juglandis, and subsequent canker formation caused by Geosmithia morbida around galleries. TCD has caused extensive morbidity and mortality to Juglans nigra in the western United States and, in 2010, was discovered in the eastern United States, where the tree is a highly valuable timber resource. WTB and G. morbida also have been found in J. regia orchards throughout major production areas in California, and the numbers of damaged trees are increasing. We tested the susceptibility of walnut and hickory species to G. morbida in greenhouse and field studies. Carya illinoinensis, C. aquatica, and C. ovata were immune. All walnut species tested, including J. ailantifolia, J. californica, J. cinerea, J. hindsii, J. major, J. mandshurica, J. microcarpa, J. nigra, and J. regia, developed cankers following inoculation with G. morbida. J. nigra was the most susceptible, whereas J. major, a native host of the WTB and, presumably, G. morbida, had smaller and more superficial cankers. Canker formation differed among maternal half-sibling families of J. nigra and J. cinerea, indicating genetic variability in resistance to G. morbida. Our inoculation studies with G. morbida have corroborated many of the field observations on susceptibility of walnut and hickory species to TCD, although the ability of the WTB to successfully attack and breed in walnut is also an important component in TCD resistance.

Nighttime parenting strategies and sleep-related risks to infants.

A large social science and public health literature addresses infant sleep safety, with implications for infant mortality in the context of accidental deaths and Sudden Infant Death Syndrome (SIDS). As part of risk reduction campaigns in the USA, parents are encouraged to place infants supine and to alter infant bedding and elements of the sleep environment, and are discouraged from allowing infants to sleep unsupervised, from bed-sharing either at all or under specific circumstances, or from sofa-sharing. These recommendations are based on findings from large-scale epidemiological studies that generate odds ratios or relative risk statistics for various practices; however, detailed behavioural data on nighttime parenting and infant sleep environments are limited. To address this issue, this paper presents and discusses the implications of four case studies based on overnight observations conducted with first-time mothers and their four-month old infants. These case studies were collected at the Mother-Baby Behavioral Sleep Lab at the University of Notre Dame USA between September 2002 and June 2004. Each case study provides a detailed description based on video analysis of sleep-related risks observed while mother-infant dyads spent the night in a sleep lab. The case studies provide examples of mothers engaged in the strategic management of nighttime parenting for whom sleep-related risks to infants arose as a result of these strategies. Although risk reduction guidelines focus on eliminating potentially risky infant sleep practices as if the probability of death from each were equal, the majority of instances in which these occur are unlikely to result in infant mortality. Therefore, we hypothesise that mothers assess potential costs and benefits within margins of risk which are not acknowledged by risk-reduction campaigns. Exploring why mothers might choose to manage sleep and nighttime parenting in ways that appear to increase potential risks to infants may help illuminate how risks occur for individual infants.

Rank and reproduction among female langur monkeys: Aging and improvement (They're not just getting older, they're getting better)

An investigation of the social rank, reproduction, and ages of adult female Indian gray langur monkeys (Presbytis entellus) living in two colony social groups revealed that rank based on displacements is neither correlated with nor best predicted by female age or reproductive value. The hierarchy of female ranks is best conceptualized as a layered ranking system in which there are clusters of females of the same dominance rank forming layers within the structure. Statistical significance in frequencies of displacement differs between but not within these layered groups of females. Factors such as group composition, presence of uterine kin, reproductive state, and individual personality are hypothesized to predict changes in female rank far better than does reproductive value. Our data show that reproductive success increases with age. The infant survival record for the six oldest females in our colony was much better than for the five youngest adult females.

There is no such thing as infant sleep, there is no such thing as breastfeeding, there is only breastsleeping.

Recently Mobbs et al. 2015 describe the need for, and benefits of, immediate and sustained contact, including cosleeping, to establish an appropriate foundation for optimal human infant breastfeeding, neonatal attachment and brain growth. To further support this model, we propose a new concept, ‘breastsleeping’, aimed to help both resolve the bedsharing debate and to distinguish the significant differences (and associated advantages) of the breastfeeding–bedsharing dyad when compared with the nonbreastfeeding–bedsharing situations, when the combination of breastfeeding–bedsharing is practiced in the absence of all known hazardous factors. Breastfeeding is so physiologically and behaviourally entwined and functionally interdependent with forms of cosleeping that we propose the use of the term breastsleeping to acknowledge the following: (i) the critical role that immediate and sustained maternal contact plays in helping to establish optimal breastfeeding; (ii) the fact that normal, human (species wide) infant sleep can only be derived from studies of breastsleeping dyads because of the ways maternal–infant contact affects the delivery of breastmilk, the milk’s ingestion, the infant’s concomitant and subsequent metabolism and other physiological processes, maternal and infant sleep architecture, including arousal patterns, as well as breastfeeding frequency and prolongation; and (iii) that breastsleeping by mother–infant pairs comprises such vastly different behavioural and physiological characteristics compared with nonbreastfeeding mothers and infants, this dyadic context must be distinguished and given its own epidemiological category and benefits to risk assessment. Incorporating evolutionary theory and natural selective processes as a powerful explanatory frame, Mobbs et al. (1) revisit a model of what attachment theorist John Bowlby (2) might have called the optimal ‘environment of evolutionary adaptedness’, within which breastfeeding evolved. Ironically, one major weakness in Bowlby’s otherwise polymathic formulation and explanation of ‘attachment’ was his seeming de-emphasis of the role that human breastmilk and breastfeeding delivery actually played in its aetiology. Instead, Bowlby emphasised the more critical consequences of an infant convincing its mother to invest in its survival, with natural selection operating to exaggerate both neonatal facial attributes (big eyes situated on the midline of the face, surrounded by round, nonangular or nonthreatening cheeks) and emotionally attractive, reflexive infantile behavioural responses such as high-pitched cooing infantile gaze, as well as infant affectional responses such as terminating cries when soothed, and infant smiling. According to Bowlby, these evolved human infantile traits, which expanded on our related suite of phylogenetic characteristics as primates, coalesced to help motivate mothers (and others) to not only breastfeed and carry but to also protect their infants from predators. In contrast, Mobbs et al. assign different priorities than did Bowlby to the initial mechanisms promoting attachment and stress the absolute centrality of breastfeeding, and, specifically, they argue for a necessary, sequential unfolding of it. Mobbs et al. argue that human neonates need from the start unhindered and immediate sustained maternal contact, including maternal–infant cosleeping, to assure maximum lactogenesis. While many other factors contribute along the way, they posit that the absence of unhindered mother–infant contact, from the outset, is a significant hindrance to breastfeeding beyond three months (3).