Use of duvets and the risk of sudden infant death syndrome

Risk Factors for Suffocation and Unexplained Causes of Infant Deaths

BACKGROUND

Observational studies have improved our understanding of the risk factors for sudden infant death syndrome, but separate examination of risk for sleep-related suffocation and unexplained infant deaths has been limited. We examined the association between unsafe infant sleep practices and sudden infant deaths (sleep-related suffocation and unexplained causes including sudden infant death syndrome).

METHODS

We conducted a population-based case-control study using 2016 to 2017 Centers for Disease Control and Prevention data. Controls were liveborn infants from the Pregnancy Risk Assessment Monitoring System; cases were from the Sudden Unexpected Infant Death Case Registry. We calculated risk factor prevalence among cases and controls and crude and adjusted odds ratios.

RESULTS

We included 112 sleep-related suffocation cases with 448 age-matched controls and 300 unexplained infant death cases with 1200 age-matched controls. Adjusted odds for sleep-related suffocation ranged from 18.7 (95% confidence interval [CI]: 6.8-51.3) among infants not sharing a room with their mother or caregiver to 1.9 (95% CI: 0.9-4.1) among infants with nonsupine sleep positioning. Adjusted odds for unexplained death ranged from 7.6 (95% CI: 4.7-12.2) among infants not sharing a room with their mother or caregiver to 1.6 (95% CI: 1.1-2.4) among nonsupine positioned infants.

COCLUSIONS

We confirmed previously identified risk factors for unexplained infant death and independently estimated risk factors for sleep-related suffocation. Significance of associations for suffocation followed similar patterns but was of larger magnitude. This information can be used to improve messaging about safe infant sleep.

Cardiorespiratory coupling in health and disease

Cardiac and respiratory activities are intricately linked both functionally as well as anatomically through highly overlapping brainstem networks controlling these autonomic physiologies that are essential for survival. Cardiorespiratory coupling (CRC) has many potential benefits creating synergies that promote healthy physiology. However, when such coupling deteriorates autonomic dysautonomia may ensue. Unfortunately there is still an incomplete mechanistic understanding of both normal and pathophysiological interactions that respectively give rise to CRC and cardiorespiratory dysautonomia. Moreover, there is also a need for better quantitative methods to assess CRC. This review addresses the current understanding of CRC by discussing: (1) the neurobiological basis of respiratory sinus arrhythmia (RSA); (2) various disease states involving cardiorespiratory dysautonomia; and (3) methodologies measuring heart rate variability and RSA.

Infant care practices related to sudden infant death syndrome in South Asian and White British families in the UK

In the UK, infants of South Asian parents have a lower rate of sudden infant death syndrome (SIDS) than White British infants. Infant care and life style behaviours are strongly associated with SIDS risk. This paper describes and explores variability in infant care between White British and South Asian families (of Bangladeshi, Indian or Pakistani origin) in Bradford, UK (the vast majority of which were Pakistani) and identifies areas for targeted SIDS intervention. A cross-sectional telephone interview study was conducted involving 2560 families with 2- to 4-month-old singleton infants enrolled in the Born in Bradford cohort study. Outcome measures were prevalence of self-reported practices in infant sleeping environment, sharing sleep surfaces, breast feeding, use of dummy or pacifier, and life style behaviours. We found that, compared with White British infants, Pakistani infants were more likely to: sleep in an adult bed (OR = 8.48 [95% CI 2.92, 24.63]); be positioned on their side for sleep (OR = 4.42 [2.85, 6.86]); have a pillow in their sleep environment (OR = 9.85 [6.39, 15.19]); sleep under a duvet (OR = 3.24 [2.39, 4.40]); be swaddled for sleep (OR = 1.49 [1.13, 1.97]); ever bed-share (OR = 2.13 [1.59, 2.86]); regularly bed-share (OR = 3.57 [2.23, 5.72]); ever been breast-fed (OR = 2.00 [1.58, 2.53]); and breast-fed for 8+ weeks (OR = 1.65 [1.31, 2.07]). Additionally, Pakistani infants were less likely to: sleep in a room alone (OR = 0.05 [0.03, 0.09]); use feet-to-foot position (OR = 0.36 [0.26, 0.50]); sleep with a soft toy (OR = 0.52 [0.40, 0.68]); use an infant sleeping bag (OR = 0.20 [0.16, 0.26]); ever sofa-share (OR = 0.22 [0.15, 0.34]); be receiving solid foods (OR = 0.22 [0.17, 0.30]); or use a dummy at night (OR = 0.40 [0.33, 0.50]). Pakistani infants were also less likely to be exposed to maternal smoking (OR = 0.07 [0.04, 0.12]) and to alcohol consumption by either parent. No difference was found in the prevalence of prone sleeping (OR = 1.04 [0.53, 2.01]). Night-time infant care therefore differed significantly between South Asian and White British families. South Asian infant care practices were more likely to protect infants from the most important SIDS risks such as smoking, alcohol consumption, sofa-sharing and solitary sleep. These differences may explain the lower rate of SIDS in this population.

Sleep and Infant Learning

Human neonates spend the majority of their time sleeping. Despite the limited waking hours available for environmental exploration, the first few months of life are a time of rapid learning about the environment. The organization of neonate sleep differs qualitatively from adult sleep, and the unique characteristics of neonatal sleep may promote learning. Sleep contributes to infant learning in multiple ways. First, sleep facilitates neural maturation, thereby preparing infants to process and explore the environment in increasingly sophisticated ways. Second, sleep plays a role in memory consolidation of material presented while the infant was awake. Finally, emerging evidence indicates that infants process sensory stimuli and learn about contingencies in their environment even while asleep. As infants make the transition from reflexive to cortically mediated control, learned responses to physiological challenges during sleep may be critical adaptations to promote infant survival.

Newborn infants learn during sleep

Newborn infants must rapidly adjust their physiology and behavior to the specific demands of the novel postnatal environment. This adaptation depends, at least in part, on the infant's ability to learn from experiences. We report here that infants exhibit learning even while asleep. Bioelectrical activity from face and scalp electrodes was recorded from neonates during an eye movement conditioning procedure in which a tone was followed by a puff of air to the eye. Sleeping newborns rapidly learned the predictive relationship between the tone and the puff. Additionally, in the latter part of training, these infants exhibited a frontally maximum positive EEG slow wave possibly reflecting memory updating. As newborns spend most of their time sleeping, the ability to learn about external stimuli in the postnatal environment during nonawake states may be crucial for rapid adaptation and infant survival. Furthermore, because eyelid conditioning reflects functional cerebellar circuitry, this method potentially offers a unique approach for early identification of infants at risk for a range of developmental disorders including autism and dyslexia.

What is the mechanism of SIDS? Clues from epidemiology

The cause of sudden infant death syndrome (SIDS) is unknown. Many mechanisms have been postulated, although thermal stress, rebreathing of expired gases and infection/inflammation seem the most viable hypotheses for the causation of SIDS. Deaths from SIDS have reduced dramatically following the recommendation not to place infants to sleep prone. Epidemiological data have shown that prone sleeping position is more risky in winter, colder latitudes, higher altitudes, if the infant is unwell or has excessive bedding or clothing. This suggests prone sleeping position involves either directly or indirectly a thermal mechanism. SIDS caused by an infective/inflammatory mechanism might be associated with deaths occurring during the night. Rebreathing of expired gases, airway obstruction, long QT syndrome and other genetic conditions may explain a small number of sudden unexpected deaths in infancy.

Sids

INTRODUCTION

By definition, the cause of sudden infant death syndrome (SIDS) is not known. Observational studies have found an association between SIDS and several risk factors, including prone sleeping position, prenatal or postnatal exposure to tobacco smoke, soft sleeping surfaces, hyperthermia/overwrapping, bed sharing (particularly with mothers who smoke), lack of breastfeeding, and lack of soother use. The risk of SIDS is increased in families in which there has been a prior sudden infant death.

METHODS AND OUTCOMES

We conducted a systematic review and aimed to answer the following clinical question: What are the effects of interventions to reduce the risk of SIDS? We searched: Medline, Embase, The Cochrane Library, and other important databases up to April 2007 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).

RESULTS

We found 28 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.

CONCLUSIONS

In this systematic review, we present information relating to the effectiveness and safety of the following interventions: advice to avoid prone sleeping; advice to avoid tobacco-smoke exposure; advice to avoid soft sleeping surfaces; advice to avoid overheating or overwrapping; advice to avoid bed sharing; advice to breastfeed; advice to promote soother/pacifier use; and advice to promote room sharing (without bed sharing).

Sleep environment risk factors for sudden infant death syndrome: the German Sudden Infant Death Syndrome Study

OBJECTIVE

Our goal was to investigate the risk factors for sudden infant death syndrome in the infants' sleep environment for a population in which few infants sleep prone as a result of education campaigns.

METHODS

This was a population-based sudden infant death syndrome case-control study over 3 years (1998-2001) in Germany.

RESULTS

There were 333 sudden infant death syndrome cases and 998 matched controls. Although only 4.1% of the infants were placed prone to sleep, those infants were at a high risk of sudden infant death syndrome. Those who were unaccustomed to sleeping prone were at very high risk, as were those who turned to prone. Bed sharing (especially for infants younger than 13 weeks); duvets; sleeping prone on a sheepskin; sleeping in the house of a friend or a relative (compared with sleeping in the parental home); and sleeping in the living room (compared with sleeping in the parental bedroom) increased the risk for sudden infant death syndrome; pacifier use during the last sleep was associated with a significantly reduced risk of sudden infant death syndrome.

CONCLUSIONS

This study has clarified the risk factors for sudden infant death syndrome in a population where few infants sleep prone. This study supports the current recommendations of the American Academy of Pediatrics. This study has identified several novel risk factors for sudden infant death syndrome: an increased risk if the infants sleeps outside the parental home, death in the living room, and the high risk when sleeping prone on a sheepskin; however, because the numbers of cases in these groups are small, additional studies are needed to confirm these findings.

The German case-control scene investigation study on SIDS: epidemiological approach and main results

The present study, which was part of the German SIDS Study (GeSID), enrolled sudden infant death syndrome (SIDS) cases and population controls and obtained objective scene data via specifically trained observers shortly after discovery of each dead infant. Infants who had died suddenly and unexpectedly at ages between 8 and 365 days were enrolled in five regions of Germany between November 1998 and October 2001. Shortly after discovery of each dead infant, a specially trained doctor of legal medicine visited the bereaved family at home. Data were obtained by measurements and observations. Dead infants underwent a standardised autopsy, additional information being obtained by standardised parent interviews. Investigation of the sleep environment and wake-up scene in matched controls followed the same protocol. A total of 52 SIDS cases and 154 controls were enrolled, 58% were boys, and median age of cases vs. controls was 126 vs. 129 days. Risk factors in the sleeping environment were pillow use (adjusted OR 4.3; 95%CI 1.6-11.6), heavy duvets (OR 4.4; 1.5-13.3), soft underlay (OR 3.0; 1.1-8.7), face covered by bedding (OR 15.8; 2.5-102.1) and entire body covered by bedding (OR 35.5; 5.5-228.3). Using a standardised protocol, including objective measurements of the sleep environment and a case-control design, this study was able to confirm many risk factors for SIDS.

Recommendations for sudden infant death syndrome prevention: a discussion document

This article reviews the evidence for the current UK Department of Health recommendations for prevention of sudden infant death syndrome (SIDS) and suggests other factors that should be considered. The wording of the Department of Health recommendations for SIDS prevention has changed over the past 6 years, but the specific recommendations are largely consistent with the scientific evidence. The emphasis on thermal and illness factors and immunisation could be reduced. Bed sharing and sharing the parental bedroom should be given more emphasis. Two major recommendations need to be discussed in greater detail: (1) breast feeding and (2) pacifier use. Meta-analyses or reviews looking at each risk factor or a combination of risk factors are required. Further, it is recommended that a committee is established that reviews the recommendations and publishes the evidence that leads to these recommendations, as is done by the American Academy of Pediatrics Taskforce on Sudden Infant Death Syndrome.

Thermal insulation and SIDS-an investigation of selected 'Eastern' and 'Western' infant bedding combinations

BACKGROUND

Differences in the incidence of SIDS between 'Western' and 'Eastern' countries has been attributed to cultural practices, which may affect the infants care and thermal environment.

AIM

The purpose of this work was to estimate for selected 'commonly' used bedding, sleep positions and practices in Japan, Korea and New Zealand, the intrinsic 'dry' thermal resistance of bedding. Insulation levels are also discussed in the context of published information about the thermal environment in which the bedding is likely to be used.

METHOD

Selected Japanese, Korean and New Zealand bedding was loosely tucked over an infant manikin in the lateral, prone and supine sleep positions. Thickness in use was measured, and intrinsic 'dry' thermal resistance estimated using the Wilson Laing model which accommodates the effect on insulation of the three-dimensional arrangement of bedding combinations during use.

RESULTS AND DISCUSSION

Thickness of under- and upper-bedding varied among countries with thickness and estimated 'dry' thermal resistance of the upper-bedding affected by the type/combination of bedding and the infants sleep position. Insulation levels are discussed in relation to environmental conditions within and among countries and between seasons. Further information on thermal environments, bedding combinations used and care practices within both Asian and Western countries is needed.

CONCLUSIONS

'Eastern' infants appear likely to be generally covered in bedding combinations of greater insulation than those used to cover 'Western' infants in comparable seasons. Differences existed between insulation of the Japanese and Korean bedding combinations investigated. Lower rates of SIDS apparent in 'Asian' populations do not appear attributable to use of lower levels of bedding insulation only.

Thermal stress in sudden infant death: Is there an ambiguity with the rebreathing hypothesis?

OBJECTIVE

To assess the role of thermal stress in the cause of sudden infant death syndrome (SIDS), and to compare risk factors with those of rebreathing.

METHODOLOGY

Analysis of publications concerning the epidemiology and physiology of thermal stress in SIDS.

RESULTS

A strong association between thermal regulation and ventilatory control was found, specifically for prolonged apnea. Infections, excessive room heat and insulation, and prone sleeping produce significantly increased odds ratios for SIDS. Although some of the risk factors for rebreathing could be explained by the effects of thermal stress, several factors for thermal stress could not reasonably be explained by the rebreathing hypothesis.

CONCLUSIONS

Although the risk of thermal stress is widely accepted abroad, it has received relatively little attention in the United States. The incidence of SIDS in the United States can likely be further reduced by educating the public against the dangers of overheating, as an integral part of the back-to-sleep campaign.

Infant stress and sleep deprivation as an aetiological basis for the sudden infant death syndrome

SIDS is almost invariably sleep-related. Viable syndrome aetiology must be compatible with its many epidemiologically diverse risk factors, each of which directly or indirectly associates with the creation of psychological and/or physiological infant stress, and the subsequent disruption of normal, contented sleep. During essential deep 'rebound' recovery sleep, arousal ability and upper airway muscle tone decrease further to that in normal sleep, with subsequent upper airway obstruction. When stress impact causes sufficient sleep disruption and physiological fatigue, a failure to arouse and so restore sufficient tone to overcome such obstruction results in sudden, unexpected death. SIDS has therefore many causes which share a final lethal mechanical pathway. Evidence is presented for obstructive apnoea during sleep as being the primary syndrome death mode, for sleep disruption, reduced arousal ability, and infant stress in SIDS, and for risk factor association with the creation of this stress. Specific infant vulnerability in the first 6 months of life to stress predominantly related to total dependency on a carer for gratification of need, and to obstructive sleep apnoea due to normal anatomical, physical, and respiratory immaturity, including rapid physiological fatigue, and peaks in sleep and thermal stress vulnerability, are discussed. Further reasons for the limited age period of SIDS, and for reduced neonatal risk, are given. Prone sleeping risk can relate to positional airway obstruction during normal sleep without prior infant stress. Much of SIDS aetiology appears to concern factors related to socio-economic deprivation and subsequent sub-optimal infant care.

CLINICAL REVIEW ARTICLE: Is changing the sleep environment enough? Current recommendations for SIDS

Sudden infant death syndrome (SIDS or cot death) was the major cause of post-neonatal infant death in many countries in the late 1970s and 1980s. There is now very strong evidence that public intervention campaigns targeting the prone sleeping position, which had been identified by epidemiological studies as a major risk factor, were followed by substantial falls in the rate of SIDS. In the present review we discuss the evidence on which current recommendations for the prevention of SIDS are based. The prone sleeping position is now clearly causally associated with SIDS. Further reductions in SIDS may be produced by recommending the back sleeping position as opposed to the side position. Maternal smoking in pregnancy and bed sharing by infants of mothers who smoke are also strongly associated with SIDS, but have been harder to influence. Paternal smoking has also been implicated, although the magnitude of the reported risk is small. Finally, breastfeeding, pacifier use and having the infant sharing the parents bedroom, but not the bed, may also reduce risk. Continued reductions in SIDS mortality will require innovative public health education to target these major risk factors, while building on the "back to sleep" approach.