Where Will the Baby Sleep? Attitudes and Practices of New and Experienced Parents Regarding Cosleeping with Their Newborn Infants

An evolutionary perspective on human infant sleep physiology suggests that parent-infant cosleeping, practiced under safe conditions, might be beneficial to both mothers and infants. However, cosleeping is not part of mainstream parenting ideology in the United States or the United Kingdom, and little evidence is available to indicate whether, and under what circumstances, parents sleep with their newborn infants. We present data from an anthropological investigation into the practices and attitudes of new and experienced parents of newborn infants regarding parent-infant sleeping arrangements in a community in the northeast of England. Despite not having contemplated cosleeping prior to the birth, new parents in our sample found it to be a convenient nighttime caregiving strategy, and one which was practiced regularly. Infants slept with both their parents, some being habitual all-night cosleepers, but commonly beginning the night in a cnb and sleeping with their parents for several hours following the early morning feed, [infant sleep, newborn, cosleeping, new parents]     

Evolution and sudden infant death syndrome (SIDS)

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. James J. McKenna is Associate Professor of Anthropology and Chair of the Department of Sociology and Anthropology at Pomona College. He also has an appointment as an Adjunct Clinical Assistant Professor in the Departments of Pediatrics, Child Psychiatry, and Human Behavior at the University of California, Irvine, School of Medicine. His primary research interests and many of his publications concern aspects of primate parenting and infant development among both human and nonhuman primates. For the past seven years he has been investigating from an anthropological perspective possible environmental correlates of the sudden infant death syndrome (SIDS) and has just finished a preliminary study on the physiological correlates of human parent-infant co-sleeping. His earlier monograph on the subject (cited in this paper) has received much international attention. He and his colleagues (Mosko and Dungy) are the first to have used standard polysomnographic techniques to document simultaneously human parent-infant co-sleeping. He has won three awards for distinguished teaching at Pomona College.     

Sleep and arousal patterns of co-sleeping human mother/infant pairs: a preliminary physiological study with implications for the study of sudden infant death syndrome (SIDS)

The prevailing research design for studying infant sleep erroneously assumes the species-wide normalcy of solitary nocturnal sleep rather than a social sleeping environment. In fact, current clinical perspectives on infant sleep, which are based exclusively on studies of solitary sleeping infants, may partly reflect culturally induced rather than species-typical infant sleep patterns which can only be gleaned, we contend here, from infants sleeping with their parents--the context within which, and for well over 4 million years, the hominid infant's sleep, breathing, and arousal patterns evolved. Our physiological study of five co-sleeping mother-infant pairs in a sleep lab is the first study of its kind to document the unfolding sleep patterns of mothers and infants sleeping in physical contact. Our data show that co-sleeping mothers and infants exhibit synchronous arousals, which, because of the suspected relationship between arousal and breathing stability in infants, have important implications for how we study environmental factors possibly related to some forms of the sudden infant death syndrome (SIDS). While our data show that co-sleeping mothers and infants also experience many moments of physiological independence from each other, it is clear that the temporal unfolding of particular sleep stages and awake periods of the mother and infant become entwined and that on a minute-to-minute basis, throughout the night, much sensory communication is occurring between them. Our research acknowledges the human infant's evolutionary past and considers the implications that nocturnal separation (a historically novel and alien experience for them) has for maternal and infant well-being in general and SIDS research strategies in particular.     

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.     

Sleeping position in infants over 6 months of age: implications for theories of sudden infant death syndrome

The aim of this study was to determine the prevalence of prone and supine sleeping in infants aged 0-12 months and relate this to changes in the number of cases of sudden infant death syndrome (SIDS) since 1985. Seventy-two babies, 38 male and 34 female, were followed for the first 18 months of life with regular home visits and sleeping position was recorded. In addition, data on the number of cases of SIDS in England and Wales between 1985 and 1995 were analysed. All babies slept supine for the first 5 months of life, but once they could turn over in their cots (mean age 7.34 months, range 5-11 months) the majority slept prone. By 11 months of age, 53 regularly slept prone (73%), 95% CI +/- 19.8%), while 11 slept supine, three adopted the side position and five varied from night to night. The number of cases of SIDS in infants aged 7-11 months has fallen significantly (P<0.0001) in a period in which the prevalence of prone sleeping, in that age group, has not changed. The most plausible explanation for this paradoxical result is that supine sleeping in the first 5 months of life reduces the absolute risk of SIDS in the second 6 months of life even though most babies are then sleeping prone. It is suggested that reduced exposure to nasopharyngeal bacterial superantigens in babies sleeping prone might explain this effect.     

Heart Rate Variability in Sleeping Preterm Neonates Exposed to Cool and Warm Thermal Conditions

Sudden infant death syndrome (SIDS) remains the main cause of postneonatal infant death. Thermal stress is a major risk factor and makes infants more vulnerable to SIDS. Although it has been suggested that thermal stress could lead to SIDS by disrupting autonomic functions, clinical and physiopathological data on this hypothesis are scarce. We evaluated the influence of ambient temperature on autonomic nervous activity during sleep in thirty-four preterm neonates (mean ± SD gestational age: 31.4±1.5 weeks, postmenstrual age: 36.2±0.9 weeks). Heart rate variability was assessed as a function of the sleep stage at three different ambient temperatures (thermoneutrality and warm and cool thermal conditions). An elevated ambient temperature was associated with a higher basal heart rate and lower short- and long-term variability in all sleep stages, together with higher sympathetic activity and lower parasympathetic activity. Our study results showed that modification of the ambient temperature led to significant changes in autonomic nervous system control in sleeping preterm neonates. The latter changes are very similar to those observed in infants at risk of SIDS. Our findings may provide greater insight into the thermally-induced disease mechanisms related to SIDS and may help improve prevention strategies.     

Evolution and the sudden infant death syndrome (SIDS)

Postnatal parent-infant physiological regulatory effects described in the previous paper (Part I) are viewed here as being biologically contiguous with events that occur prenatally, preparing and sensitizing the fetus to the average microenvironment into which the infant is expected, based on its evolutionary past, to be born. Following McKenna (1986), evidence (some of which is circumstantial) is presented concerning fetal hearing and fetal amniotic liquid breathing as they are affected both by maternal cardiovascular blood flow sounds in the uterus and by fluctuating maternal blood sugar levels. These data are linked in turn to the infant’s postulated postnatal responsivity to parental sensory cues, including auditory and vestibular respiratory cues that may assist infants as they “learn” to breathe and, for some, to resist a SIDS event. Data on the respiratory and vocalizing behavior of normal and hearing-impaired persons are used to show that not all forms of human breathing are innate; some forms develop with experience. These data reveal how human infants learn, for example, to coordinate higher and lower brain respiratory nuclei in the context of learning initially to cry with intent and purpose and later to speak. Voluntary, cortex-based breathing emerges at the same time that infants are most likely to die from SIDS, between 2 and 4 months of age. This switch between voluntary and involuntary breathing during both sleep (while dreaming) and wake cycles, which depends on the integration of higher cortical and lower brain stem nuclei, is complex and is possibly the basis of the human species’ unique susceptibility to SIDS—a syndrome as yet unrecognized in other species. These human infant vulnerabilities, including delayed maturity, can explain in part why natural selection ought to favor increased infant sensitivity to parental sensory cues provided by a caregiver—stimuli available in the evolving parental care environment that included parent-infant co-sleeping for more than 4–5 million years of human evolution.     

Nighttime Wakefulness Associated with Infant Rearing in Callithrix kuhlii

Parent-infant cosleeping occurs in human and nonhuman primates, yet studies on the impact of cosleeping on parental sleep patterns have been limited to human mothers. We examined the effects of cosleeping on the nighttime wakefulness of a biparental New World primate, Wied's black tufted-ear marmoset (Callithrix kuhlii). We compared the sleep patterns of marmoset parents caring for young infants to those without infants, using an 8 mm videocamera and timelapse VCR under infrared illumination. The presence of young infants significantly impacted the sleep of mothers but not fathers. In fact, mothers rearing young infants were awake >3 times as often as mothers without infants. We also examined the nighttime wakefulness of marmoset parents across the first 9 weeks of infant life (birth through weaning). Although callitrichid mothers tend to reduce their daytime investment in offspring very early in infant life by relinquishing the care of infants to fathers and alloparents, increased nighttime wakefulness was not limited to the early postpartum period for the mothers. Instead, mothers exhibited more nighttime wakefulness than fathers did across the first 9 weeks of infant life. Our results indicate that the presence of infants has a greater impact on the sleep patterns of Callithrix kuhlii mothers than fathers, suggesting that mothers are more involved in infant care than previously realized and that fathers are not nearly as involved in nighttime care as their behavior during the day would suggest.     

Sudden infant death syndrome and Canadian Aboriginals: bacteria and infections

Aboriginal populations in Canada, America and Australia have higher incidences of sudden infant death syndrome (SIDS) than non-Aboriginal groups. Canadian Aboriginal populations (known also as first nation, native or Indian) experience infant morbidity/mortality rates 3-7 times that of non-Aboriginals, with upper track respiratory infection and SIDS recorded as the leading causes. The aim of this investigation was to examine the home environment of Aboriginal infants, particularly during winter months when respiratory tract infections and SIDS are more common. Environmental bacteria, fungi and air particulates were examined in the residences of Aboriginal infants during visits to individual homes on an Aboriginal reserve. The physical histories of SIDS victims were gathered from medical files. Air and surfaces were sampled by agar strips which were processed by a commercial laboratory. The levels of fungi, bacteria and air particulate rates recorded in the reserve homes of Aboriginal infants registered levels considered to be detrimental to the health of the inhabitants. Such extreme levels could contribute to the high incidence of respiratory disease and SIDS experienced by Canadian Aboriginal infants.     

The nasopharyngeal bacterial flora in infancy: effects of age, gender, season, viral upper respiratory tract infection and sleeping position

The aim of the investigation was to determine the effect of age, gender, viral upper respiratory tract infection (URTI), season and sleeping position on the composition of the nasopharyngeal bacterial flora in infancy. Seventy-two babies, 38 male and 34 female, whose birthdates were evenly spread throughout the year were followed from birth to 18 months of age. From 0 to 6 months nasopharyngeal swabs were obtained once a month in periods without URTI and daily for 3 days during episodes of URTI. From 12 to 18 months of age nasopharyngeal swabs were obtained in the early morning alter an overnight sleep and later in the day after the baby had been up for over 2 h. Swabs were obtained in prone and supine sleepers with and without infection. In infants aged 0-6 months URTI had little effect on the nasopharyngeal bacterial flora, but there was a marked effect of age and less marked effect of season and gender. In particular Staphylococcus aureus carriage decreased with age, was most common in the winter months and the density of colonisation was greater in males than females. In infants aged 12-18 months the combination of prone sleeping with URTI and an early morning swab led to increased carriage of staphylococci, streptococci. Haemophilus influenzae and Gram-negative bacilli which are not normally part of the nasopharyngeal flora. These results are relevant to sudden infant death syndrome (SIDS). The combination of prone sleeping and URTI reproduces the nasopharyngeal flora seen in SIDS. Gram-negative bacilli isolated from SIDS cases should not be dismissed as post-mortem contaminants. The features of S. aureus make it a prime candidate for a pathogenic role in SIDS.     

The development of behavioural sex differences in infant rhesus macaques (Macaca mulatta)

Studies of infant rhesus macaques have generally reported sex differences in the frequency of expression of some behaviour patterns, such as rough-and-tumble play and socio-sexual mounting. In contrast, sex differences in other behaviour patterns, such as proximity to the mother, have been less consistantly reported. Using data on the behavioural development of infant rhesus macaques living in captive social groups, we have attempted to provide further evidence for, or against, sex differences in behaviour and to investigate the possible influence of maternal rank and parity on sex differences in infant behaviour and mother-infant interactions. The behaviour of 14 male and 20 female infants and their mothers was studied during the first six months of life, including measures of play behaviour socio-sexual mounting, and mother-infant interactions. Our data reveal that, on average, male infants exhibited more rough-and-tumble play and mounting than female infants, and also exhibited stationary play, chasing play, and initiated play more frequently than females. Such sex differences appear to be robust in macaques and have been reported in a variety of housing conditions. male and female infants did not differ in the amount of time spent at particular distances from their mothers, and mothers were not found to behave differently towards sons and daughters, using measures of restraint, rejection, and grooming. These results are in contrast to previous studies on singly-housed mother-infant pairs but similar to those on free-ranging populations. Mothers did behave differently towards their infants depending upon the mother's rank and previous number of offspring. These maternal characteristics may have significant consequences for the behavioural development of both male and female infant primates.     

Infant care in the spectral tarsier ( Tarsius spectrum ) Sulawesi, Indonesia

I present quantitative and qualitative data on infant caretaking behaviors collected during a preliminary field study of spectral tarsiers (Tarsius spectrum),in a northern Sulawesi rain forest. The primary goal of the study is to identify the basic pattern of infant care in this species. I studied tarsiers at Tangkoko-Dua Saudara Nature Reserve in Sulawesi, Indonesia, from May to July 1992. I observed two infants, from two groups for a total of 96 hr using focal follows. During individual focal follows, ranging from 20 min to 6 hr, I recorded behaviors at 5-min intervals. I also recorded distances of group members relative to the infant at 5-min intervals. I subsampled the data at 35-min intervals to control for statistical autocorrelation between data points. Infants were alone between 40 and 50% of the time. The two subadults were more frequently in proximity to the infant than the adult males, the nonmatemal adult female, or the mothers were. This pattern of the subadults maintaining proximity to the infant continued when the mothers were absent. These results suggest that subadults may be guarding or babysitting infants. It is also possible that subadults are not traveling as far from the sleeping site as adults do and are therefore more likely to be found in association with the infant.     

Infant care in the spectral tarsier (Tarsius spectrum) Sulawesi,Indonesia

I present quantitative and qualitative data on infant caretaking behaviors collected during a preliminary field study of spectral tarsiers (Tarsius spectrum),in a northern Sulawesi rain forest. The primary goal of the study is to identify the basic pattern of infant care in this species. I studied tarsiers at Tangkoko-Dua Saudara Nature Reserve in Sulawesi, Indonesia, from May to July 1992. I observed two infants, from two groups for a total of 96 hr using focal follows. During individual focal follows, ranging from 20 min to 6 hr, I recorded behaviors at 5-min intervals. I also recorded distances of group members relative to the infant at 5-min intervals. I subsampled the data at 35-min intervals to control for statistical autocorrelation between data points. Infants were alone between 40 and 50% of the time. The two subadults were more frequently in proximity to the infant than the adult males, the nonmatemal adult female, or the mothers were. This pattern of the subadults maintaining proximity to the infant continued when the mothers were absent. These results suggest that subadults may be guarding or babysitting infants. It is also possible that subadults are not traveling as far from the sleeping site as adults do and are therefore more likely to be found in association with the infant.     

Cortisol levels and control of inflammatory responses to toxic shock syndrome toxin-1 (TSST-1): the prevalence of night-time deaths in sudden infant death syndrome (SIDS)

There is evidence that inflammatory responses have been induced in the tissues and body fluids of many SIDS infants. We suggested that some of these deaths are due to uncontrolled inflammatory responses to infectious agents and possibly cigarette smoke. The majority of SIDS deaths occur during the 2-4 month age range when infants have decreasing levels of maternal antibodies to infectious agents. Most deaths occur during the early hours of the morning. Adults are more susceptible to inflammatory responses at night due to lower levels of cortisol associated with circadian rhythm patterns. Infants develop these patterns between the ages of 7 weeks and 4 months, at which time their night-time cortisol levels drop dramatically. The objective of this study was to use an in vitro model system to assess the effects of different cortisol levels on proinflammatory cytokine production in response to the staphylococcal toxic shock syndrome toxin-1 (TSST-1) which has been identified in a significant number of SIDS infants. Levels of cortisol present in infants at night and during the day before and after the development of the circadian rhythm pattern were examined. Human buffy coats (n = 9) were stimulated with TSST-1 and responses assessed over 72 hours by a bioassay for tumour necrosis factor-alpha (TNF-alpha) and an enzyme linked immunosorbent assay (ELISA) for interleukin-6 (IL-6). Cortisol levels present in an infant at night after development of circadian rhythm (< or = 5 microg dl(-1)), did not significantly increase or decrease production of either TNF-alpha or IL-6. Concentrations of cortisol greater than 5 microg dl(-1) usually found in infants during the day or at night prior to the physiological change significantly decreased production of TNF-alpha at 12 hours and of IL-6 at 12 and 16 hours. Only cortisol levels greater than 5 microg dl(-1) significantly decreased production of the pro-inflammatory cytokines by human buffy coats stimulated with TSST-1. If the switch to the circadian rhythm pattern occurs in an infant when maternal antibodies are still present or after they have developed their own active immunity, the infant could neutralise common viruses, toxins or bacteria: however, if this switch occurs in an infant when antibody levels are low, this could be a window of vulnerability during which infants are at an increased risk of death if uncontrolled inflammatory responses are induced by infectious agents or their products.     

The protective effect of immunisation against diphtheria, pertussis and tetanus (DPT) in relation to sudden infant death syndrome

Epidemiological evidence indicates infants immunised against diphtheria, pertussis and tetanus (DPT) are at decreased risk of sudden infant death syndrome (SIDS). Asymptomatic whooping cough and pyrogenic toxins of Staphylococcus aureus have been implicated in the aetiology of SIDS. The objectives of the present study were: (1) to determine if the DPT vaccine induced antibodies cross-reactive with the staphylococcal toxins; (2) to determine if antibodies to the pertussis toxin (PT) and the staphylococcal toxins were present in the sera of women during late pregnancy; (3) to examine the effects of infant immunisation on levels of antibodies to PT and the staphylococcal toxins; (4) to assess the effects of changes in immunisation schedules in the UK on the incidence and age distribution of SIDS. Enzyme-linked immunosorbent assays (ELISA) were used to measure binding of rabbit or human IgG to the DPT vaccine, PT, toxic shock syndrome toxin-1 (TSST-1) and staphylococcal enterotoxins A (SEA), B (SEB) and C (SEC). Neutralisation activity of anti-DPT serum was assessed by a bioassay for induction of nitric oxide from human monocytes by the staphylococcal toxins. Anti-DPT serum bound to the DPT vaccine, PT and each of the staphylococcal toxins. It also reduced the ability of the four toxins to induce nitric oxide from monocytes. In pregnant women, levels of IgG to PT, SEC and TSST-1 decreased significantly in relation to increasing weeks of gestation while antibodies to SEA and SEB increased. In infants' sera there were significant correlations between levels of IgG bound to DPT and IgG bound to PT, TSST-1 and SEC but not SEA or SEB. Antibody levels to the toxins in infants declined with age; sera from infants < or = 2 months of age had higher levels of IgG bound to the toxins than those older than 2 months. This pattern was observed for infants whose immunisation schedules began at 2 months of age or 3 months of age. The decrease in IgG bound to the toxins was, however, less for those immunised at 2 months. The decrease in SIDS deaths after the change in immunisation schedules was greatest in the 4-6-month age range. While DPT immunisation might prevent some unexplained infant deaths due to asymptomatic whooping cough, these data indicate that immunisation with DPT also induces antibodies cross-reactive with pyrogenic staphylococcal toxins implicated in many cases of SIDS. Passive immunisation of infants who have low levels of these antibodies might reduce further the numbers of these infant deaths.     

Inflammatory responses in sudden infant death syndrome – past and present views

Sudden infant death syndrome (SIDS) is sudden unexpected death in infancy for which there is no explanation based on commonly accepted diagnostic criteria; however, half of the victims have had slight signs of infection prior to death. Such slight infection with fever is an important risk factor in combination with a prone sleeping position, especially in infants between 2 and 4 months of age. The purpose of this review is to summarise findings that support the theory that a significant part of cot deaths may be due to an overreaction to otherwise harmless infections. Such factors are mucosal immune stimulation, cytokines in the cerebrospinal fluid and hypoxanthine levels in vitreous humour. The review aims at explaining why we believe that a slight infection combined with a prone position, a warm environment and a vulnerable age period may trigger a vicious circle leading to death.     

Endotoxin in blood and tissue in the sudden infant death syndrome

Although the explanation for sudden infant death syndrome (SIDS) remains unknown, an increasing body of evidence now exists to suggest a possible role for bacterial toxins in the aetiology, and a number of investigators have considered that endotoxaemia could explain some of the associated features. Following the development of an animal model which confirmed that endotoxaemia could be detected after death, we studied endotoxin levels in blood and tissue samples taken at autopsy from SIDS infants, child controls and adult controls. There were significant correlations between endotoxin levels in blood and the various organs sampled particularly in SIDS cases and child controls, and blood endotoxin levels in SIDS cases were higher in those infants where there was histological evidence of mild to moderate inflammation. However, overall no significant differences were found between endotoxin levels in blood or tissue in the three study groups. Further studies into possible actions or interactions of endotoxin in SIDS are required.     

The protective effect of breast feeding in relation to sudden infant death syndrome (SIDS): II. The effect of human milk and infant formula preparations on binding of Clostridium perfringens to epithelial cells

Breast feeding is known to protect an infant against gastrointestinal pathogens and epidemiological studies indicate that compared to breast fed infants, formula fed infants are at a greater risk of dying from sudden infant death syndrome (SIDS). Many SIDS infants have symptoms of gastrointestinal infections prior to death and one gastrointestinal pathogen associated with SIDS is Clostridium perfringens. Studies have found that a significantly higher number of formula fed SIDS infants have C perfringens and its enterotoxin in their faeces compared to breast fed infants. The aim of the study was to compare the effects of human milk and infant formula on binding of C perfringens to epithelial cells. Two protocols were used to assess the effect of human milk and infant formula to inhibit binding of C perfringens to epithelial cells. Binding was assessed by flow cytometry. For the in vivo protocol which more closely represents interactions on the mucosal surface, breast milk enhanced bacterial binding but infant formula caused inhibition of binding; however for the in vitro method, both human milk and infant formula resulted in consistent enhancement of binding. Flow cytometry studies indicated that enhancement of binding was due to the formation of bacterial aggregates. Lewis(a) and Lewis(b) antigens, found in both breast milk and infant formula, inhibited C. perfringens binding in a dose dependent manner. The Lewis(a) and Lewis(b) antigens in human milk and infant formula can inhibit C. perfringens binding to epithelial cells. While infant formula reduced binding of C. perfringens to epithelial cells in the experiments carried out with the in vivo protocol, the protective effects of breast feeding in relation to colonisation with C. perfringens are more likely to be due to formation of bacterial aggregates. These findings have implications for improving infant formula preparations.     

Change in immunisation schedule and sudden infant death syndrome in Hungary

Infant mortality in Hungary was higher than in other European countries; however, the reported incidence of sudden infant death syndrome (SIDS) has been lower than those for Western Europe and the United States. Childhood immunisation has been reported to be a protective factor for SIDS. In Britain, the change to an earlier immunisation schedule for diphtheria, pertussis, and tetanus appeared to be associated with a shift in the age distribution of SIDS. In 1999, immunisation for Haemophilus influenzae type b (Hib) was introduced for Hungarian infants at the age of 2 months. Data for total infant mortality and SIDS in Hungary were analysed between 1990 and 2002. Infection was the major cause of death among Hungarian infants followed by SIDS. Following introduction of Hib immunisation, there was a decrease in deaths due to meningitis from an average of 3.5% of all infant deaths between 1990 and 1998 to an average of 1% of all infant deaths between 1999 and 2002 (p=0.00). There was also a significant decrease in the proportion of SIDS in the age range > or =2 months from 48% in the earlier period to 39% after introduction of the vaccine (p=0.03). The decrease in SIDS might be due in part to decrease in unrecognised Hib infections or to induction of antibodies by the tetanus toxoid to which the Hib polysaccharide is conjugated that are cross reactive with bacterial toxins implicated in SIDS.     

Differences in CO2 threshold of respiratory muscles in preterm infants

Because neonatal apnea is frequently associated with airway obstruction, we compared relative changes in activity between various upper airway muscles and the diaphragm during hypercapnic stimulation. The technique of hyperoxic CO2 rebreathing was employed in 17 healthy, sleeping preterm infants studied at a postnatal age of 32 +/- 12 days. Surface diaphragm (DIA) electromyograms (EMGs) were recorded in all infants, and noninvasive measurements of posterior cricoarytenoid (PCA), genioglossus (GG), and alae nasi (AN) EMGs were analyzed in 11, 9, and 8 infants, respectively. During the control period, consistent phasic EMGs were recorded from the DIA in all infants and from the PCA in 8 infants, but from the GG and AN each in only one infant. During CO2 rebreathing, minute ventilation and end-tidal CO2 increased linearly as CO2 rose from 31 +/- 5 to 51 +/- 5 Torr. DIA and PCA EMGs also had proportional and comparable increases throughout rebreathing. In contrast, both GG and AN responses differed from the DIA and PCA (P less than 0.001) and exhibited minimal or absent responses at low levels of hypercapnia. Consistent GG and AN EMGs appeared at comparable levels of end-tidal CO2 (47 +/- 5 and 45 +/- 5 Torr, respectively) and subsequently increased linearly in most infants. We conclude that during CO2 rebreathing the initially delayed and subsequently linear responses of the GG and AN EMGs indicate a high CO2 threshold for these muscles.