Reasons mothers bedshare: A review of its effects on infant behavior and development.

Bedsharing is controversial for nighttime caregiving in the U.S. today, as in most of the West. However, from the standpoint of evolutionary pediatrics, anthropology, and cultural psychology, bedsharing is not controversial at all, representing the context for human infant evolution and conferring a host of physiological benefits to the infant as well as the mother. In an effort to understand the rise in Western bedsharing in recent decades (and following Ball, 2002; McKenna & Volpe, 2007), Salm Ward (2015) systematically reviewed the literature on mother-infant bedsharing and identified ten reasons why mothers choose to bedshare: (1) breastfeeding, (2) comforting for mother or infant, (3) better/more sleep for infant or parent, (4) monitoring, (5) bonding/ attachment, (6) environmental reasons, (7) crying, (8) cultural or familial traditions, (9) disagree with danger, and (10) maternal instinct. The current paper offers the "review behind the review," highlighting the scientific evidence behind the reasons mothers give for their decision to bedshare, focusing on how mothers' decisions about infant sleep location influence infant behavior and development.

US fathers' reports of bonding, infant temperament and psychosocial stress based on family sleep arrangements.

BACKGROUND AND OBJECTIVES: Evolutionary-grounded sleep research has been critical to establishing the mutual dependence of breastfeeding and nighttime sleep proximity for mothers and infants. Evolutionary perspectives on cosleeping also often emphasize the emotional motivations for and potential benefits of sleep proximity, including for parent-infant bonding. However, this potential link between infant sleep location and bonding remains understudied for both mothers and fathers. Moreover, in Euro-American contexts bedsharing has been linked to family stress and difficult child temperament, primarily via maternal reports. We know relatively little about whether paternal psychosocial dynamics differ based on family sleep arrangements, despite fathers and other kin often being present in the cosleeping environment across cultures. Here, we aim to help address some of these gaps in knowledge pertaining to fathers and family sleep arrangements. METHODOLOGY: Drawing on a sample of Midwestern U.S. fathers (N=195), we collected sociodemographic and survey data to analyze links between infant nighttime sleep location, paternal psychosocial well-being, father-infant bonding, and infant temperament. From fathers' reports, families were characterized as routinely solitary sleeping, bedsharing, or roomsharing (without bedsharing). RESULTS: We found that routinely roomsharing or bedsharing fathers, respectively, reported stronger bonding than solitary sleepers. Bedsharing fathers also reported that their infants had more negative temperaments and also tended to report greater parenting-related stress due to difficulties with their children. CONCLUSIONS: These cross-sectional results help to highlight how a practice with deep phylogenetic and evolutionary history, such as cosleeping, can be variably expressed within communities with the potential for family-dependent benefits or strains.

Bedsharing and Breastfeeding: The Academy of Breastfeeding Medicine Protocol #6, Revision 2019.

A central goal of the Academy of Breastfeeding Medicine is the development of clinical protocols for managing common medical problems that may impact breastfeeding success. These protocols serve only as guidelines for the care of breastfeeding mothers and infants and do not delineate an exclusive course of treatment or serve as standards of medical care. Variations in treatment may be appropriate according to the needs of an individual patient.

An Integrated Analysis of Maternal-Infant Sleep, Breastfeeding, and Sudden Infant Death Syndrome Research Supporting a Balanced Discourse.

Breastfeeding and the place of sleep for the mother and the infant have been controversial internationally due to reported concerns regarding infant deaths despite the known benefits of exclusive and prolonged breastfeeding, which are increased by breastfeeding at night. The aims of this integrated analysis were to (a) review breastfeeding and maternal and infant sleep research literature via historical, epidemiological, anthropological, and methodological lenses; (b) use this information to determine where we are currently in safeguarding both infant lives and breastfeeding; and (c) postulate the direction that research might take from this point forward to improve our knowledge and inform our policy and practice. Despite well-meaning but unsuccessful campaigns in some countries to dissuade parents from sleeping with their babies, many breastfeeding mothers and caregivers do sleep with their infants whether intentionally or unintentionally. Taking cultural contexts and socio-ecological circumstances into consideration, data supports policies to counsel parents and caregivers on safe sleep practices, including bed-sharing in non-hazardous circumstances, particularly in the absence of parental smoking, recent parental alcohol consumption, or sleeping next to an adult on a sofa. Further research with appropriate methodology is needed to drill down on actual rates of infant deaths, paying close attention to the definitions of deaths, the circumstances of the deaths, and confounding factors, in order to ensure we have the best information with which to derive public health policy. Introduction and use of the concept of "breastsleeping" is a plausible way to remove the negative connotations of "co-sleeping" and redirect ongoing data-driven discussions and education of best practices of breastfeeding and sleep.

Testosterone moderates the effects of social support on cardiovascular disease risk factors among older US men.

OBJECTIVES: Social support positively affects health through pathways such as shaping intrapersonal emotional and psychological well-being. Lower testosterone often interrelates with psychological and behavioral orientations that are beneficial to participation in emotionally supportive relationships. Yet, little research has considered the ways in which testosterone may contribute to health outcomes related to emotional support. METHODS: We draw on testosterone, social support data, and cardiovascular disease (CVD)-relevant indicators (inflammatory markers; blood pressure [BP]) from older men (n = 366) enrolled in the National Health and Nutrition Examination Survey, a US nationally representative study. We test whether men's testosterone moderates associations between emotional social support and markers related to CVD risk. RESULTS: For men with relatively lower testosterone, higher levels of social support predicted lower white blood cell (WBC) counts, consistent with reduced inflammation. In contrast, men with higher testosterone exhibited elevated WBC counts with greater support. In a diverging pattern, men with lower testosterone had higher systolic and diastolic BP with higher support, whereas the slopes for systolic and diastolic BP, respectively, were comparatively flatter for men with higher levels of testosterone. CONCLUSIONS: We suggest that our findings are theoretically consistent with the idea that testosterone helps shape intrapersonal and interpersonal experiences and perceptions of men's emotional support networks, thereby affecting the health implications of that support. The somewhat divergent results for WBC count vs BP highlight the need for inclusion of other neuroendocrine markers alongside testosterone as well as refined measures of perceived and received support.

Infant co-sleeping patterns and maternal sleep quality among Hadza hunter-gatherers.

OBJECTIVE: Despite widespread interest in maternal-infant co-sleeping, few quantified data on sleep patterns outside of the cultural west exist. Here, we provide the first report on co-sleeping behavior and maternal sleep quality among habitually co-sleeping hunter-gatherers. DESIGN: Data were collected among the Hadza of Tanzania who live in domiciles constructed of grass huts with no access to synthetic lighting or climate controlled sleeping environments. Using interview data, we recorded baseline ethnographic data on co-sleeping. Using actigraph data, we tested whether sleep quality, sleep-wake activity, and/or sleep duration differs among breastfeeding women, non-breastfeeding women, and men. MEASUREMENTS: CamNtech Motionwatch 8 actigraphs were used to collect 1 minute, epoch-by-epoch data on a sample of 33 adults. Functional linear modeling (FLM) was used to characterize sleep-wake patterns and a linear mixed-effects model was used to assess factors that drive sleep duration and quality. RESULTS: The FLM suggests that breastfeeding mothers were early risers and had reduced day-time activity. Additionally, total number of co-sleepers, not breastfeeding, was associated with less sleep duration and quality, suggesting that greater number of co-sleepers may be a primary driver of poorer sleep. CONCLUSION: The current study makes important contributions to the cross-cultural literature on sleep and augments our understanding of maternal-infant co-sleeping. The majority of Hadza participants co-sleep with at least one other individual and the majority of married couples sleep with their spouse and their children on the same sleeping surface. Our preliminary sleep quality data suggest that breastfeeding does not negatively impact maternal sleep quality.

Adiposity, CVD risk factors and testosterone: Variation by partnering status and residence with children in US men.

Background and objectives: In many settings, partnered, invested fathers have lower testosterone than single men or fathers who are not involved in caregiving. Reduced testosterone has been identified as a risk factor for multiple chronic diseases, and men's health also commonly varies by life history status. There have been few tests of whether variation in testosterone based on partnering and parenting has implications for men's health. Methodology: We analysed data from a US population-representative sample (NHANES) of young-to-middle aged US men (n = 875; mean age: 29.8 years ± 6.0 [SD]). We tested for life history status differences in testosterone, adiposity levels and biomarkers of cardiovascular disease (CVD)-risk (HDL cholesterol; triglycerides; white blood cell count [WBC]). Results: Partnered men residing with children (RC) had lower testosterone and elevated abdominal adiposity compared to never married men not residing with children. While they did not significantly differ for WBC or triglycerides, partnered RC men also had comparatively lower HDL. Partnered RC males' lower testosterone accounted for their relatively elevated adiposity, but testosterone, adiposity, and health-related covariates did not explain their relatively reduced HDL. Conclusions and implications: Our results linking life history status-based differences in testosterone and adiposity, alongside our complementary HDL findings, indicate that testosterone-related psychobiology might have implications for partnered RC men's CVD risk in the US and other similar societal settings. These types of socially contextualized observations of men's health and physiological function particularly merit incorporation in clinical discussions of fatherhood as a component of men's health.

Translating human biology (introduction to special issue).

OBJECTIVES: Introducing a special issue on "Translating Human Biology," we pose two basic questions: Is human biology addressing the most critical challenges facing our species? How can the processes of translating our science be improved and innovated? METHODS: We analyze articles published in American Journal of Human Biology from 2004-2013, and find there is very little human biological consideration of issues related to most of the core human challenges such as water, energy, environmental degradation, or conflict. There is some focus on disease, and considerable focus on food/nutrition. We then introduce this special volume with reference to the following articles that provide exemplars for the process of how translation and concern for broader context and impacts can be integrated into research. CONCLUSIONS: Human biology has significant unmet potential to engage more fully in translation for the public good, through consideration of the topics we focus on, the processes of doing our science, and the way we present our domain expertise.

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.

Does cosleeping contribute to lower testosterone levels in fathers? Evidence from the Philippines.

Because cross-species evidence suggests that high testosterone (T) may interfere with paternal investment, the relationships between men's transition to parenting and changes in their T are of growing interest. Studies of human males suggest that fathers who provide childcare often have lower T than uninvolved fathers, but no studies to date have evaluated how nighttime sleep proximity between fathers and their offspring may affect T. Using data collected in 2005 and 2009 from a sample of men (n = 362; age 26.0 ± 0.3 years in 2009) residing in metropolitan Cebu, Philippines, we evaluated fathers' T based on whether they slept on the same surface as their children (same surface cosleepers), slept on a different surface but in the same room (roomsharers), or slept separately from their children (solitary sleepers). A large majority (92%) of fathers in this sample reported practicing same surface cosleeping. Compared to fathers who slept solitarily, same surface cosleeping fathers had significantly lower evening (PM) T and also showed a greater diurnal decline in T from waking to evening (both p<0.05). Among men who were not fathers at baseline (2005), fathers who were cosleepers at follow-up (2009) experienced a significantly greater longitudinal decline in PM T over the 4.5-year study period (p<0.01) compared to solitary sleeping fathers. Among these same men, baseline T did not predict fathers' sleeping arrangements at follow-up (p>0.2). These results are consistent with previous findings indicating that daytime father-child interaction contributes to lower T among fathers. Our findings specifically suggest that close sleep proximity between fathers and their offspring results in greater longitudinal decreases in T as men transition to fatherhood and lower PM T overall compared to solitary sleeping fathers.

Evolutionary perspectives on mother-infant sleep proximity and breastfeeding in a laboratory setting.

Human maternal and infant biology likely coevolved in a context of close physical contact and some approximation of frequent, "infant-initiated" breastfeeding. Still, mothers and infants commonly sleep apart from one another in many western societies, indicating a possible "mismatch" between cultural norms and infant biology. Here we present data from a 3-night laboratory-based study that examines differences in mother-infant sleep physiology and behavior when mothers and infants sleep together on the same surface (bedsharing) and apart in separate rooms (solitary). We analyze breastfeeding frequency and interval data from the first laboratory night (FN) for 52 complementary breastfeeding mothers and infants (26 total mother-infant pairs), of which 12 pairs were routine bedsharers (RB) and 14 were routine solitary sleepers (RS). RB infants were 12.0 ± 2.7 (SD) weeks old; RS infants were 13.0 ± 2.4 weeks old. On the FN, RB mother-infant pairs (while bedsharing) engaged in a greater number of feeds per night compared to RS (while sleeping alone) (P < 0.001). RB also showed lower intervals (min) between feeds relative to RS (P < 0.05). When we evaluated data from all three laboratory nights (n = 36), post hoc, RB breastfed significantly more often (P < 0.01) and showed a trend towards lower intervals between feeds (P < 0.10). Given the widely known risks associated with little or no breastfeeding, the demonstrated mutually regulatory relationship between bedsharing and breastfeeding should be considered in future studies evaluating determinants of breastfeeding outcomes.

Mother-infant cosleeping, breastfeeding and sudden infant death syndrome: what biological anthropology has discovered about normal infant sleep and pediatric sleep medicine.

Twenty years ago a new area of inquiry was launched when anthropologists proposed that an evolutionary perspective on infancy could contribute to our understanding of unexplained infant deaths. Here we review two decades of research examining parent-infant sleep practices and the variability of maternal and infant sleep physiology and behavior in social and solitary sleeping environments. The results challenge clinical wisdom regarding "normal" infant sleep, and over the past two decades the perspective of evolutionary pediatrics has challenged the supremacy of pediatric sleep medicine in defining what are appropriate sleep environments and behaviors for healthy human infants. In this review, we employ a biocultural approach that integrates diverse lines of evidence in order to illustrate the limitations of pediatric sleep medicine in adopting a view of infants that prioritizes recent western social values over the human infant's biological heritage. We review what is known regarding infant sleeping arrangements among nonhuman primates and briefly explore the possible paleoecological context within which early human sleep patterns and parent-infant sleeping arrangements might have evolved. The first challenges made by anthropologists to the pediatric and SIDS research communities are traced, and two decades of studies into the behavior and physiology of mothers and infants sleeping together are presented up to the present. Laboratory, hospital and home studies are used to assess the biological functions of shared mother-infant sleep, especially with regard to breastfeeding promotion and SIDS reduction. Finally, we encourage other anthropologists to participate in pediatric sleep research using the unique skills and insights anthropological data provide. By employing comparative, evolutionary and cross-cultural perspectives an anthropological approach stimulates new research insights that influence the traditional medical paradigm and help to make it more inclusive. That this review will potentially stimulate similar research by other anthropologists is one obvious goal. That this article might do so makes it ever more possible that anthropologically inspired work on infant sleep will ultimately lead to infant sleep scientists, pediatricians, and parents becoming more informed about the consequences of caring for human infants in ways that are not congruent with their evolutionary biology.

Why babies should never sleep alone: a review of the co-sleeping controversy in relation to SIDS, bedsharing and breast feeding.

There has been much controversy over whether infants should co-sleep or bedshare with an adult caregiver and over whether such practises increase the risk of SIDS or fatal accident. However, despite opposition from medical authorities or the police, many western parents are increasingly adopting night-time infant caregiving patterns that include some co-sleeping, especially by those mothers who choose to breast feed. This review will show that the relationships between infant sleep patterns, infant sleeping arrangements and development both in the short and long term, whether having positive or negative outcomes, is anything but simple and the traditional habit of labelling one sleeping arrangement as being superior to another without an awareness of family, social and ethnic context is not only wrong but possibly harmful. We will show that there are many good reasons to insist that the definitions of different types of co-sleeping and bedsharing be recognised and distinguished. We will examine the conceptual issues related to the biological functions of mother-infant co-sleeping, bedsharing and what relationship each has to SIDS. At very least, we hope that the studies and data described in this paper, which show that co-sleeping at least in the form of roomsharing especially with an actively breast feeding mother saves lives, is a powerful reason why the simplistic, scientifically inaccurate and misleading statement 'never sleep with your baby' needs to be rescinded, wherever and whenever it is published.