Are risk factors for sudden infant death syndrome different at night?

Death from Failed Protection? An Evolutionary-Developmental Theory of Sudden Infant Death Syndrome

Sudden infant death syndrome (SIDS) has been mainly described from a risk perspective, with a focus on endogenous, exogenous, and temporal risk factors that can interact to facilitate lethal outcomes. Here we discuss the limitations that this risk-based paradigm may have, using two of the major risk factors for SIDS, prone sleep position and bed-sharing, as examples. Based on a multipronged theoretical model encompassing evolutionary theory, developmental biology, and cultural mismatch theory, we conceptualize the vulnerability to SIDS as an imbalance between current physiologic-regulatory demands and current protective abilities on the part of the infant. From this understanding, SIDS appears as a developmental condition in which competencies relevant to self-protection fail to develop appropriately in the future victims. Since all of the protective resources in question are bound to emerge during normal infant development, we contend that SIDS may reflect an evolutionary mismatch situation-a constellation in which certain modern developmental influences may overextend the child's adaptive (evolutionary) repertoire. We thus argue that SIDS may be better understood if the focus on risk factors is complemented by a deeper appreciation of the protective resources that human infants acquire during their normal development. We extensively analyze this evolutionary-developmental theory against the body of epidemiological and experimental evidence in SIDS research and thereby also address the as-of-yet unresolved question of why breastfeeding may be protective against SIDS.

Ventilatory response to added dead space in infants exposed to second-hand smoke in pregnancy

Maternal cigarette smoking in pregnancy can adversely affect infant respiratory control. In utero nicotine exposure has been shown to blunt the infant ventilatory response to hypercapnia, which could increase the risk of sudden infant death syndrome. The potential impact of maternal second-hand smoke exposure, however, has not yet been determined. The aim of this study was to assess ventilatory response to added dead-space (inducing hypercapnia) in infants with second-hand smoke exposure during pregnancy, in infants whose mothers smoked and in controls (non-smoke exposed). Infants breathed through a face mask and specialised "tube-breathing" circuit, incorporating a dead space of 4.4 ml/kg body weight. The maximum minute ventilation (MMV) during added dead space breathing was determined and the time taken to achieve 63% of the MMV calculated (the time constant (TC) of the response). Infants were studied on the postnatal ward prior to discharge home. Thirty infants (ten in each group) were studied with a median gestational age of 39 [range 37-41] weeks, birthweight of 3.1 [2.2-4.0] kg, and postnatal age of 33 (21-62) h. The infants whose mothers had second-hand smoke exposure (median TC 42 s, p = 0.001), and the infants of cigarette smoking mothers (median TC 37 s, p = 0.002) had longer time constants than the controls (median TC 29 s). There was no significant difference between the TC of the infants whose mothers had second-hand smoke exposure and those whose mothers smoked (p = 0.112).    Conclusion: Second-hand smoke exposure during pregnancy was associated with a delayed newborn ventilatory response. What is Known: • Maternal cigarette smoking in pregnancy can adversely affect infant respiratory control. • The potential impact of maternal second-hand smoke exposure, however, has not yet been determined. What is New: • We have assessed the ventilatory response to added dead-space (inducing hypercapnia) in newborns with second-hand smoke exposure during pregnancy, in infants whose mothers smoked, and in controls (non-smoke exposed). • Maternal second-hand smoke exposure, as well as maternal smoking, during pregnancy was associated with a delayed newborn ventilatory response.

Evidence Base for 2022 Updated Recommendations for a Safe Infant Sleeping Environment to Reduce the Risk of Sleep-Related Infant Deaths

Every year in the United States, approximately 3500 infants die of sleep-related infant deaths, including sudden infant death syndrome (SIDS) (International Statistical Classification of Diseases and Related Health Problems 10th Revision [ICD-10] R95), ill-defined deaths (ICD-10 R99), and accidental suffocation and strangulation in bed (ICD-10 W75). After a substantial decline in sleep-related deaths in the 1990s, the overall death rate attributable to sleep-related infant deaths have remained stagnant since 2000, and disparities persist. The triple risk model proposes that SIDS occurs when an infant with intrinsic vulnerability (often manifested by impaired arousal, cardiorespiratory, and/or autonomic responses) undergoes an exogenous trigger event (eg, exposure to an unsafe sleeping environment) during a critical developmental period. The American Academy of Pediatrics recommends a safe sleep environment to reduce the risk of all sleep-related deaths. This includes supine positioning; use of a firm, noninclined sleep surface; room sharing without bed sharing; and avoidance of soft bedding and overheating. Additional recommendations for SIDS risk reduction include human milk feeding; avoidance of exposure to nicotine, alcohol, marijuana, opioids, and illicit drugs; routine immunization; and use of a pacifier. New recommendations are presented regarding noninclined sleep surfaces, short-term emergency sleep locations, use of cardboard boxes as a sleep location, bed sharing, substance use, home cardiorespiratory monitors, and tummy time. In addition, additional information to assist parents, physicians, and nonphysician clinicians in assessing the risk of specific bed-sharing situations is included. The recommendations and strength of evidence for each recommendation are published in the accompanying policy statement, which is included in this issue.

Maternal Smoking, Alcohol and Recreational Drug Use and the Risk of SIDS Among a US Urban Black Population

BACKGROUND

Rates of sudden infant death syndrome (SIDS) are twice as high among Black infants compared to white infants in the US. While the contribution of sleep environment factors to this disparity is known, little is known about the risk of SIDS among Black infants in relation to maternal prenatal smoking, alcohol and drug use as well as infant smoke exposure.

OBJECTIVE

To assess the contribution of maternal substance use during pregnancy and the potential interactions with infant bedsharing in a high-risk, urban Black population.

METHODS

The Chicago Infant Mortality Study (CIMS) collected data on 195 Black infants who died of SIDS and 195 controls matched on race, age and birthweight. Risk of SIDS was calculated for maternal smoking, alcohol and drug use, adjusting for potential confounding variables and other risk factors for SIDS. Interactions between these substance use variables and bedsharing were also calculated.

RESULTS

Infants were more likely to die from SIDS if the mother smoked during pregnancy (aOR 3.90, 95% CI 1.37-3.30) and post-pregnancy (aOR 2.49, 95% CI 1.49-4.19). There was a dose response seen between amount smoked during pregnancy and risk of SIDS. Use of alcohol (aOR 2.89, 95% CI 1.29-6.99), cocaine (aOR 4.78, 95% CI 2.45-9.82) and marijuana (aOR 2.76, 95% CI 1.28-5.93) were associated with increased risk of SIDS. In the final, multivariable model controlling for sociodemographic factors and covariates, maternal smoking (aOR 3.03, 95% CI 1.03-8.88) and cocaine use (aOR 4.65, 95% CI 1.02-21.3) during pregnancy remained significant. There were significant, positive interactions between bedsharing and maternal smoking during pregnancy and post-pregnancy, alcohol use and cocaine use.

CONCLUSION

Maternal use of tobacco, alcohol and cocaine during pregnancy is associated with significantly increased risk of SIDS in a Black, urban population. Reducing substance use and eliminating disparities in SIDS, sudden unexpected infant death (SUID) (also known as sudden unexpected death in infancy or SUDI) and infant mortality need to involve more than individual level education, but instead will require a comprehensive examination of the role of social determinants of health as well as a multi-pronged approach to address both maternal and infant health and wellbeing.

Circadian variation in sudden unexpected infant death in the United States

Aim

To determine which factors are associated with sudden unexpected infant death (SUID) by time of day.

Methods

Data were analysed from the National Fatality Review Case Reporting System (2006‐2015). Out of 20 005 SUID deaths in 37 states, 12 191 (60.9%) deaths had a recorded nearest hour of discovery of the infant. We compared distribution patterns between time of death and 118 variables to determine which were significantly correlated with SUID time of death using advanced statistical modelling techniques.

Results

The 12‐hour time periods that were most different were 10:00 to 21:00 (daytime) and 22:00 to 09:00 (nighttime). The main features that were associated with nighttime SUID were bed sharing, younger infants, non‐white infants, placed supine to sleep and found supine, and caregiver was the parent. Daytime SUID was associated with older infants, day care, white infants, sleeping in an adult bed and prone sleep position. Factors not associated with time of death were sex of the infant, smoking and breastfeeding.

Conclusion

Sudden unexpected infant death deaths that occur at night are associated with a separate set of risk factors compared to deaths that occur during the day. However, to minimise risk, it is important to practice safe sleep guidelines during both nighttime and daytime sleep.

Beyond "Back to Sleep": Ways to Further Reduce the Risk of Sudden Infant Death Syndrome

Sudden infant death syndrome (SIDS) remains the leading cause of postneonatal mortality in the United States, despite reduction in rates of more than 50% since the initiation of the "Back to Sleep" (now called "Safe to Sleep") campaign in 1994. In recent years, the rate of decline in SIDS deaths has plateaued, even with the ongoing educational efforts that promote safe sleep and other risk reduction measures. The 2016 American Academy of Pediatrics guidelines for reducing the risk of SIDS focus heavily on sleep practices, bedding, and location, but also include factors that often receive less attention (ie, prenatal care, maternal smoking, alcohol and drug use, and childhood vaccinations). This review describes these factors that are less often addressed and identifies interventions that have resulted in positive behavioral changes that not only benefit infants, but also promote the health and well-being of their mothers. [Pediatr Ann. 2017;46(8):e284-e290.].

SIDS and Other Sleep-Related Infant Deaths: Evidence Base for 2016 Updated Recommendations for a Safe Infant Sleeping Environment

Approximately 3500 infants die annually in the United States from sleep-related infant deaths, including sudden infant death syndrome (SIDS), ill-defined deaths, and accidental suffocation and strangulation in bed. After an initial decrease in the 1990s, the overall sleep-related infant death rate has not declined in more recent years. Many of the modifiable and nonmodifiable risk factors for SIDS and other sleep-related infant deaths are strikingly similar. The American Academy of Pediatrics recommends a safe sleep environment that can reduce the risk of all sleep-related infant deaths. Recommendations for a safe sleep environment include supine positioning, use of a firm sleep surface, room-sharing without bed-sharing, and avoidance of soft bedding and overheating. Additional recommendations for SIDS risk reduction include avoidance of exposure to smoke, alcohol, and illicit drugs; breastfeeding; routine immunization; and use of a pacifier. New evidence and rationale for recommendations are presented for skin-to-skin care for newborn infants, bedside and in-bed sleepers, sleeping on couches/armchairs and in sitting devices, and use of soft bedding after 4 months of age. In addition, expanded recommendations for infant sleep location are included. The recommendations and strength of evidence for each recommendation are published in the accompanying policy statement, "SIDS and Other Sleep-Related Infant Deaths: Updated 2016 Recommendations for a Safe Infant Sleeping Environment," which is included in this issue.

Antenatal substance misuse and smoking and newborn hypoxic challenge response

OBJECTIVES

Infants of smoking (S) and substance misusing (SM) mothers have an increased risk of sudden infant death syndrome. The aim of this study was to test the hypothesis that infants of SM or S mothers compared with infants of non-SM, non-smoking mothers (controls) would have a poorer ventilatory response to hypoxia, which was particularly marked in the SM infants.

DESIGN

Physiological study.

SETTING

Tertiary perinatal centre.

PATIENTS

21 SM; 21 S and 19 control infants. Infants were assessed before maternity/neonatal unit discharge.

INTERVENTIONS

Maternal and infant urine samples were tested for cotinine, cannabinoids, opiates, amphetamines, methadone, cocaine and benzodiazepines.

MAIN OUTCOME MEASURES

During quiet sleep, the infants were switched from breathing room air to 15% oxygen and changes in minute volume were assessed.

RESULTS

The SM infants had a greater mean increase (p=0.028, p=0.034, respectively) and a greater magnitude of decline (p<0.001, p=0.018, respectively) in minute volume than the S infants and the controls. The rate of decline in minute volume was greater in the SM infants (p=0.008) and the S infants (p=0.011) compared with the controls.

CONCLUSIONS

Antenatal substance misuse and smoking affect the infant's ventilatory response to a hypoxic challenge.

Ventilatory response to hypercarbia in newborns of smoking and substance-misusing mothers

RATIONALE

Infants of mothers who smoked (S) or substance misused (SM) during pregnancy have an increased risk of sudden infant death syndrome (SIDS).

OBJECTIVES

To test the hypothesis that infants of S and SM mothers compared with infants of non-substance-misusing, nonsmoking mothers (control subjects) would have a reduced ventilatory response to hypercarbia and that any reduction would be greater in the SM infants.

METHODS

Infants were assessed before maternity/neonatal unit discharge. Maternal and infant urine samples were obtained and tested for cotinine, cannabinoids, opiates, amphetamines, methadone, cocaine, and benzodiazepines.

MEASUREMENTS AND MAIN RESULTS

Respiratory flow and Vt were measured using a pneumotachograph inserted into a face mask placed over the infant's mouth and nose. The ventilatory responses to three levels of inspired carbon dioxide (0 [baseline], 2, and 4% CO2) were assessed. Twenty-three SM, 34 S, and 22 control infants were assessed. The birth weight of the control subjects was higher than the SM and S infants (P = 0.017). At baseline, SM infants had a higher respiratory rate (P = 0.003) and minute volume (P = 0.007) compared with control subjects and S infants. Both the SM and S infants had a lower ventilatory response to 2% (P < 0.001) and 4% (P < 0.001) CO2 than the control subjects. The ventilatory response to CO2 was lower in the SM infants compared with the S infants (P = 0.009).

CONCLUSIONS

These results are consistent with infants of smoking mothers and substance misuse/smoking mothers having a dampened ventilatory response to hypercarbia, which is particularly marked in the latter group.

Diurnal and twenty-four hour patterning of human diseases: cardiac, vascular, and respiratory diseases, conditions, and syndromes

Various medical conditions, disorders, and syndromes exhibit predictable-in-time diurnal and 24 h patterning in the signs, symptoms, and grave nonfatal and fatal events, e.g., respiratory ones of viral and allergic rhinorrhea, reversible (asthma) and non-reversible (bronchitis and emphysema) chronic obstructive pulmonary disease, cystic fibrosis, high altitude pulmonary edema, and decompression sickness; cardiac ones of atrial premature beats and tachycardia, paroxysmal atrial fibrillation, 3rd degree atrial-ventricular block, paroxysmal supraventricular tachycardia, ventricular premature beats, ventricular tachyarrhythmia, symptomatic and non-symptomatic angina pectoris, Prinzmetal vasospastic variant angina, acute (non-fatal and fatal) incidents of myocardial infarction, sudden cardiac arrest, in-bed sudden death syndrome of type-1 diabetes, acute cardiogenic pulmonary edema, and heart failure; vascular and circulatory system ones of hypertension, acute orthostatic postprandial, micturition, and defecation hypotension/syncope, intermittent claudication, venous insufficiency, standing occupation leg edema, arterial and venous branch occlusion of the eye, menopausal hot flash, sickle cell syndrome, abdominal, aortic, and thoracic dissections, pulmonary thromboembolism, and deep venous thrombosis, and cerebrovascular transient ischemic attack and hemorrhagic and ischemic stroke. Knowledge of these temporal patterns not only helps guide patient care but research of their underlying endogenous mechanisms, i.e., circadian and others, and external triggers plus informs the development and application of effective chronopreventive and chronotherapeutic strategies.

Is "Bed Sharing" Beneficial and Safe during Infancy? A Systematic Review

Background. There is conflicting evidence regarding the safety and efficacy of bed sharing during infancy-while it has been shown to facilitate breastfeeding and provide protection against hypothermia, it has been identified as a risk factor for SIDS. Methods. A systematic search of major databases was conducted. Eligible studies were observational studies that enrolled infants in the first 4 weeks of life and followed them up for a variable period of time thereafter. Results. A total of 21 studies were included. Though the quality of evidence was low, bed sharing was found to be associated with higher breastfeeding rates at 4 weeks of age (75.5% versus 50%, OR 3.09 (95% CI 2.67 to 3.58), P = 0.043) and an increased risk of SIDS (23.3% versus 11.2%, OR 2.36 (95% CI 1.97 to 2.83), P = 0.025). Majority of the studies were from developed countries, and the effect was almost consistent across the studies. Conclusion. There is low quality evidence that bed sharing is associated with higher breast feeding rates at 4 weeks of age and an increased risk of SIDS. We need more studies that look at bed sharing, breast feeding, and hazardous circumstance that put babies at risk.

Maternal smoking and increased risk of sudden infant death syndrome: a meta-analysis

Maternal smoking is detrimental to the development of fetuses and neonates. This meta-analysis was performed to measure the accumulated association of sudden infant death syndrome (SIDS) risk with both prenatal and postnatal maternal smoking. The odds ratio (OR) corresponding to the 95% confidence interval (CI) was used to assess the associations between maternal smoking and SIDS risk. The statistical heterogeneity among studies was assessed with the Q-test and I(2) statistics. The data for this meta-analysis were available from 35 case-control studies. The prenatal and postnatal maternal smoking was associated with a significantly increased risk of SIDS (OR=2.25, 95% CI=2.03-2.50 for prenatal maternal smoking analysis, and OR=1.97, 95% CI=1.77-2.19 for postnatal maternal smoking analysis, respectively) by random effects model. After stratified analyses, regardless of prenatal or postnatal smoking, heavy cigarette consumption increased the risk of SIDS and significantly elevated SIDS risk was found to be associated with co-sleeping with postnatal smoking mothers. Our results suggested that maternal smoking were associated with elevated SIDS risk, the effects were dose-dependent. In addition, SIDS risk was significantly increased in infants co-sleeping with postnatal smoking mothers.

Prone sleeping position increases the risk of SIDS in the day more than at night

BACKGROUND

SIDS mortality is higher during the night than in the day.

AIM

(1) To examine risk factors for SIDS by time of day and (2) to see if the proportion of deaths at night has changed from prior to the 'Back to Sleep' campaign, which recommended infants sleep supine.

METHODS

A large population-based SIDS matched case-control (GeSID) study conducted from 1998 to 2001 (when the prevalence of infants placed prone to sleep was 4.1%). The reference sleep of the controls was matched for the estimated time of death for the case. Risk factors for SIDS were examined for night-time and day-time deaths. The estimated time of death was compared with that from an earlier study in Germany (1990-1994 when prevalence of prone sleeping was 32.2%).

RESULTS

There were 333 SIDS cases and 998 matched controls. The increased risk with placed prone to sleep was significantly different during the day [adjusted OR = 18.15 (95% CI = 5.91-55.69)] compared with during the night [adjusted OR = 3.49 (95% CI = 1.46-8.39; p-value for interaction = 0.011)]. There was no significant difference in the other risk factors examined by time of day in the multivariate analysis. The mean time found dead was 09:07. In the earlier study the mean time found dead was 08:54 and the difference was not significant (p = 0.57).

CONCLUSIONS

This study confirms previous observations that prone sleeping position carries a greater risk during the day than at night. However, the reduction in infants sleeping prone has not been associated with a reduced number of deaths in the day in Germany.

Sudden Infant Death Syndrome and parental smoking

Prenatal exposure to tobacco smoke is a major risk factor associated with Sudden Infant Death Syndrome (SIDS) and the risk has increased despite continued advice against this practice. Evidence from the UK suggests the prevalence of maternal smoking during pregnancy has risen amongst SIDS mothers (from 50% to 80%) when the rate amongst expectant mothers in the general population has fallen (from 30% to 20%) confirming pooled estimates from recent studies of a four-fold risk. An additional risk from postnatal exposure has also been identified; increasing with the number of smokers in the household or the daily hours the infant is subjected to a smoke-filled environment. Exposure may lead to a complex range of effects upon normal physiological and anatomical development in fetal and postnatal life that places infants at greatly increased risk of SIDS. Recent legislation prohibiting smoking in public places needs to emphasise the adverse effects of tobacco smoke exposure to infants and amongst pregnant women.

Sudden Infant Death Syndrome and the time of death: factors associated with night-time and day-time deaths

OBJECTIVE

To investigate the diurnal occurrence of Sudden Infant Death Syndrome (SIDS) and interaction with established risk factors in the infant sleeping environment.

METHODS

A 3 year population-based case-control study, in five English Health Regions. Parentally defined day-time or night-time deaths of 325 SIDS infants and reference sleep of 1300 age-matched controls.

RESULTS

The majority of SIDS deaths (83%) occurred during night-time sleep, although this was often after midnight and at least four SIDS deaths occurred during every hour of the day. The length of time from last observed alive until the discovery of death ranged from <l to 14 h but was not significantly different from the corresponding sleep period amongst the controls. Amongst the day-time deaths, 38% of the infants were observed alive 30 min prior to discovery and 9% within 10 min. The risk of placing infants asleep on their side was more marked for day-time deaths (interaction: P = 0.0001) nearly half of whom were found prone, while the risk associated with paternal smoking [OR = 3.25 (95%CI: 1.88-5.62)] was more marked for night-time deaths (interaction: P = 0.02). The adverse effect of unsupervised sleep recognized for night-time practice [OR = 5.38 (95%CI: 2.67-10.85)] was also significant for day-time sleep [OR = 10.57 (95%CI: 1.47-75.96)]. Significantly more (P = 0.002) unobserved SIDS infants (24.8%) were found with bedclothes over the head compared with those SIDS infants where a parent was present in the room (11.3%).

CONCLUSIONS

SIDS can happen at any time of the day and relatively quickly. Parents need to be made aware that placing infants supine and keeping them under supervision is equally important for day-time sleeps.

Dampened ventilatory response to added dead space in newborns of smoking mothers

BACKGROUND

Term newborns can compensate fully for an imposed dead space (tube breathing) by increasing their minute ventilation.

OBJECTIVE

To test the hypothesis that infants of smoking mothers would have an impaired response to tube breathing.

DESIGN

Prospective study.

SETTING

Perinatal service.

PATIENTS

Fourteen infants of smoking and 24 infants of non-smoking mothers (median postnatal age 37 (11-85) hours and 26 (10-120) hours respectively) were studied.

INTERVENTIONS

Breath by breath minute volume was measured at baseline and when a dead space of 4.4 ml/kg was incorporated into the breathing circuit.

MAIN OUTCOME MEASURES

The maximum minute ventilation during tube breathing was determined and the time constant of the response calculated.

RESULTS

The time constant of the infants of smoking mothers was longer than that of the infants of non-smoking mothers (median (range) 37.3 (22.2-70.2) v 26.2 (13.8-51.0) seconds, p = 0.016). Regression analysis showed that maternal smoking status was related to the time constant independently of birth weight, gestational or postnatal age, or sex (p = 0.018).

CONCLUSIONS

Intrauterine exposure to smoking is associated with a dampened response to tube breathing.