Sudden Infant Death Syndrome (SIDS): State of the Art and Future Directions

Sudden infant death syndrome (SIDS) is a type of death that occurs suddenly and without any apparent explanation, affecting infants between 28 days of life and up to a year. Recognition of this entity includes performing an autopsy to determine if there is another explanation for the event and performing both an external and internal examination of the different tissues to search for possible histopathological findings. Despite the relative success of awareness campaigns and the implementation of prevention measures, SIDS still represents one of the leading causes of death among infants worldwide. In addition, although the development of different techniques has made it possible to make significant progress in the characterization of the etiopathogenic mechanisms underlying SIDS, there are still many unknowns to be resolved in this regard and the integrative consideration of this syndrome represents an enormous challenge to face both from a point of view scientific and medical view as humanitarian. For all these reasons, this paper aims to summarize the most relevant current knowledge of SIDS, exploring from the base the characterization and recognition of this condition, its forensic findings, its risk factors, and the main prevention measures to be implemented. Likewise, an attempt will be made to analyze the causes and pathological mechanisms associated with SIDS, as well as potential approaches and future paths that must be followed to reduce the impact of this condition.

Identification of bacterial pathogens in sudden unexpected death in infancy and childhood using 16S rRNA gene sequencing

Background

Sudden unexpected death in infancy (SUDI) is the most common cause of post-neonatal death in the developed world. Following an extensive investigation, the cause of ~40% of deaths remains unknown. It is hypothesized that a proportion of deaths are due to an infection that remains undetected due to limitations in routine techniques. This study aimed to apply 16S rRNA gene sequencing to post-mortem (PM) tissues collected from cases of SUDI, as well as those from the childhood equivalent (collectively known as sudden unexpected death in infancy and childhood or SUDIC), to investigate whether this molecular approach could help identify potential infection-causing bacteria to enhance the diagnosis of infection.

Methods

In this study, 16S rRNA gene sequencing was applied to de-identified frozen post-mortem (PM) tissues from the diagnostic archive of Great Ormond Street Hospital. The cases were grouped depending on the cause of death: (i) explained non-infectious, (ii) infectious, and (iii) unknown.

Results and conclusions

In the cases of known bacterial infection, the likely causative pathogen was identified in 3/5 cases using bacterial culture at PM compared to 5/5 cases using 16S rRNA gene sequencing. Where a bacterial infection was identified at routine investigation, the same organism was identified by 16S rRNA gene sequencing. Using these findings, we defined criteria based on sequencing reads and alpha diversity to identify PM tissues with likely infection. Using these criteria, 4/20 (20%) cases of unexplained SUDIC were identified which may be due to bacterial infection that was previously undetected. This study demonstrates the potential feasibility and effectiveness of 16S rRNA gene sequencing in PM tissue investigation to improve the diagnosis of infection, potentially reducing the number of unexplained deaths and improving the understanding of the mechanisms involved.

The psychological consequences of Sudden Infant Death Syndrome (SIDS) for the family system: A systematic review

The Sudden Infant Death Syndrome (SIDS) is a tragic and difficult experience for families. It involves not only the death of the baby but also the loss of a future as a parent, sibling or grandparent. The subsequent grief is multifaceted and each family member has different needs and resources. Through a systematic review of literature, we identified 24 studies between 1982 and 2021: they dealt with individual, family and couple experience when a SIDS occurs; in addition, some studies compared perinatal loss and neonatal loss with SIDS loss. Our results point out the need for an intervention that focuses on the needs of each family member and tailored around the specifics of SIDS loss rather than general grief.

Infant Safe Sleep Knowledge, Attitudes, and Behaviors by Physicians at an Academic Children's Hospital

Sudden unexpected infant death (SUID) is the leading cause of death for infants. Physician advice on safe sleep is an important source of information for families. We sought to evaluate the safe sleep knowledge, attitudes, and behaviors of physicians by distributing a cross-sectional survey at a freestanding children's hospital. The survey included demographics, knowledge items, attitudinal assessment, and frequency of providing safe sleep guidance. Multivariable linear regression and logistic regression were used to evaluate associations between variables. 398 physicians were surveyed with 124 responses (31%). Females, those who received safe sleep training, and those who see infants in daily practice had higher knowledge scores. Physicians with higher knowledge scores had more positive attitudes toward safe sleep and provided safe sleep education to patients more often. Our study underlies the importance of education and repeated exposure in forming positive attitudes toward safe sleep recommendations and leads to increased provision of safe sleep guidance.

Sudden unexpected infant death risk profiles in the first month of life

BACKGROUND

Limited improvement in current SUID rates requires further identification of its characteristics, including age-specific risk patterns.

OBJECTIVE

Compare SUID risk factors in the first week versus the remainder in the first month of life.

DESIGN/METHODS

We compared maternal and infant data from New Jersey databases for SUID from 2000 to 2015 in infants ≥ 34 weeks GA in the two groups.

RESULTS

In the period studied, 123 died in the first 27 days, 24 before seven. Deaths in the first week had a higher percentage of mothers with post-High School education (OR 3.50, CI: 1.38-8.87) and a primary Cesarean section delivery (OR 4.0, CI: 1.39-11.49), and a smaller percentage with inadequate prenatal care (OR 0.36, CI: 0.14, 0.94). A smaller percentage of first-week deaths had mothers who smoked during pregnancy or identified as Black, non-Hispanic, but these findings did not reach significance (p < .08 and p < .09, respectively).

CONCLUSIONS

SUID in the first week and the first month of life is rare. However, despite a limited sample size, data suggest that even within the first month of life, there are differences in risk patterns for SUID based on age at death. Age-specific profiles may lead to new hypotheses regarding causality and more refined risk-reduction guidelines and warrant further study.

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.

Heart Rate Variability Analysis to Evaluate Autonomic Nervous System Maturation in Neonates: An Expert Opinion

While heart rate variability (HRV) is a relevant non-invasive tool to assess the autonomic nervous system (ANS) functioning with recognized diagnostic and therapeutic implications, the lack of knowledge on its interest in neonatal medicine is certain. This review aims to briefly describe the algorithms used to decompose variations in the length of the RR interval and better understand the physiological autonomic maturation data of the newborn. Assessing newborns' autonomous reactivity can identify dysautonomia situations and discriminate children with a high risk of life-threatening events, which should benefit from cardiorespiratory monitoring at home. Targeted monitoring of HRV should provide an objective reflection of the newborn's intrinsic capacity for cardiorespiratory self-regulation.

Infants' Sleep: Israeli Parents' Knowledge, Attitudes and Practices

The purpose of the study was to assess Israeli parents' knowledge of and attitudes towards practices promoting infants' safe sleep and their compliance with such practices. Researchers visited the homes of 335 parents in 59 different residential locations in Israel and collected their responses to structured questionnaires. SPSS 25 statistical package for data analysis was used. Attitude scales were created after the reliability tests and scaled means of parental attitudes were compared between independent groups differentiated by gender, ethnicity, and parental experience. A logistic regression was run to predict the outcome variable of babies' sleep positions. The total knowledge score was significantly higher for women (56.3%) than for men (28.6%; p < 0.001). Arabs were more committed to following recommendations (29.3%) than Jews (26.9%; p < 0.001). Consistent with safe sleep recommendations, 92% of the sampled parents reported avoiding bedsharing and 89% reported using a firm mattress and fitted sheets. The risk of not placing a baby to sleep in a supine position was higher among older parents (adjusted odds ratio-AOR = 0.36, 95%CI 0.16-0.82), smoking fathers (AOR = 2.66, 95%CI 1.12-6.33), parents who did not trust recommendations (AOR = 4.03, 95%CI 1.84-8.84), parents not committed to following recommendations (AOR = 2.83, 95%CI 1.21-6.60), and parents whose baby slept in their room (AOR = 0.38, 95%CI 0.17-0.88). Knowledge of safe sleep recommendations was not associated with actual parental practices. Trust of and commitment to recommendations were positively correlated with safe sleep position practices. It is essential to develop ethnic-/gender-focused intervention programs.

The Genetics of Sudden Infant Death Syndrome-Towards a Gene Reference Resource

Sudden infant death syndrome (SIDS) is the unexpected death of an infant under one year of age that remains unexplained after a thorough investigation. Despite SIDS remaining a diagnosis of exclusion with an unexplained etiology, it is widely accepted that SIDS can be caused by environmental and/or biological factors, with multiple underlying candidate genes. However, the lack of biomarkers raises questions as to why genetic studies on SIDS to date are unable to provide a clearer understanding of the disease etiology. We sought to improve the identification of SIDS-associated genes by reviewing the SIDS genetic literature and objectively categorizing and scoring the reported genes based on the strength of evidence (from C1 (high) to C5 (low)). This was followed by analyses of function, associations between genes, the enrichment of gene ontology (GO) terms, and pathways and gender difference in tissue gene expression. We constructed a curated database for SIDS gene candidates consisting of 109 genes, 14 of which received a category 4 (C4) and 95 genes received the lowest category of C5. That none of the genes was classified into the higher categories indicates the low level of supporting evidence. We found that genes of both scoring categories show distinct networks and are highly diverse in function and involved in many GO terms and pathways, in agreement with the perception of SIDS as a heterogeneous syndrome. Genes of both scoring categories are part of the cardiac system, muscle, and ion channels, whereas immune-related functions showed enrichment for C4 genes. A limited association was found with neural development. Overall, inconsistent reports and missing metadata contribute to the ambiguity of genetic studies. Considering those parameters could help improve the identification of at-risk SIDS genes. However, the field is still far from offering a full-pledged genetic test to identify at-risk infants and is still hampered with methodological challenges and misunderstandings of the vulnerabilities of vital biological mechanisms.

Revisiting the Neuropathology of Sudden Infant Death Syndrome (SIDS)

Background: Sudden infant death syndrome (SIDS) is one of the leading causes of infant mortality in the United States (US). The extent to which SIDS manifests with an underlying neuropathological mechanism is highly controversial. SIDS correlates with markers of poor prenatal and postnatal care, generally rooted in the lack of access and quality of healthcare endemic to select racial and ethnic groups, and thus can be viewed in the context of health disparities. However, some evidence suggests that at least a subset of SIDS cases may result from a neuropathological mechanism. To explain these issues, a triple-risk hypothesis has been proposed, whereby an underlying biological abnormality in an infant facing an extrinsic risk during a critical developmental period SIDS is hypothesized to occur. Each SIDS decedent is thus thought to have a unique combination of these risk factors leading to their death. This article reviews the neuropathological literature of SIDS and uses machine learning tools to identify distinct subtypes of SIDS decedents based on epidemiological data.

Methods: We analyzed US Period Linked Birth/Infant Mortality Files from 1990 to 2017 (excluding 1992–1994). Using t-SNE, an unsupervised machine learning dimensionality reduction algorithm, we identified clusters of SIDS decedents. Following identification of these groups, we identified changes in the rates of SIDS at the state level and across three countries.

Results: Through t-SNE and distance based statistical analysis, we identified three groups of SIDS decedents, each with a unique peak age of death. Within the US, SIDS is geographically heterogeneous. Following this, we found low birth weight and normal birth weight SIDS rates have not been equally impacted by implementation of clinical guidelines. We show that across countries with different levels of cultural heterogeneity, reduction in SIDS rates has also been distinct between decedents with low vs. normal birth weight.

Conclusions: Different epidemiological and extrinsic risk factors exist based on the three unique SIDS groups we identified with t-SNE and distance based statistical measurements. Clinical guidelines have not equally impacted the groups, and normal birth weight infants comprise more of the cases of SIDS even though low birth weight infants have a higher SIDS rate.

The EASE Project Revisited: Improving Safe Sleep Practices in Ohio Birthing and Children's Hospitals

Literature has shown hospitalized infants are not often observed in recommended safe sleep environments. Our objective was to implement a quality improvement program to improve compliance with appropriate safe sleep practices in both children's and birthing hospitals. Hospitalists from both settings were recruited to join an Ohio American Academy of Pediatrics collaborative to increase admitted infant safe sleep behaviors. Participants used a standardized tool to audit infants' sleep environments. Each site implemented 3 PDSA (Plan-Do-Study-Act) cycles to improve safe sleep behaviors. A total of 37.0% of infants in children's hospitals were observed to follow the current American Academy of Pediatrics recommendations at baseline; compliance improved to 59.6% at the project's end (P < .01). Compliance at birthing centers was 59.3% and increased to 72.5% (P < .01) at the collaborative's conclusion. This study demonstrates that a quality improvement program in different hospital settings can improve safe sleep practices. Infants in birthing centers were more commonly observed in appropriate sleep environments than infants in children's hospitals.

Neonatal circumcision and prematurity are associated with sudden infant death syndrome (SIDS)

BACKGROUND

Sudden infant death syndrome (SIDS) is the most common cause of postneonatal unexplained infant death. The allostatic load hypothesis posits that SIDS is the result of cumulative perinatal painful, stressful, or traumatic exposures that tax neonatal regulatory systems.

AIMS

To test the predictions of the allostatic load hypothesis we explored the relationships between SIDS and two common phenotypes, male neonatal circumcision (MNC) and prematurity.

METHODS

We collated latitudinal data from 15 countries and 40 US states sampled during 2009 and 2013. We used linear regression analyses and likelihood ratio tests to calculate the association between SIDS and the phenotypes.

RESULTS

SIDS mortality rate was significantly and positively correlated with MNC. Globally (weighted): Increase of 0.06 (95% CI: 0.01-0.1, t = 2.86, p = 0.01) per 1000 SIDS mortality per 10% increase in circumcision rate. US (weighted): Increase of 0.1 (95% CI: 0.03-0.16, t = 2.81, p = 0.01) per 1000 unexplained mortality per 10% increase in circumcision rate. US states in which Medicaid covers MNC had significantly higher MNC rates (χ̄ = 0.72 vs 0.49, p = 0.007) and male/female ratio of SIDS deaths (χ̄ = 1.48 vs 1.125, p = 0.015) than other US states. Prematurity was also significantly and positively correlated with MNC. Globally: Increase of 0.5 (weighted: 95% CI: 0.02-0.086, t = 3.37, p = 0.004) per 1000 SIDS mortality per 10% increase in the prematurity rates. US: Increase of 1.9 (weighted: 95% CI: 0.06-0.32, t = 3.13, p = 0.004) per 1000 unexplained mortalities per 10% increase in the prematurity rates. Combined, the phenotypes increased the likelihood of SIDS.

CONCLUSIONS

Epidemiological analyses are useful to generate hypotheses but cannot provide strong evidence of causality. Biological plausibility is provided by a growing body of experimental and clinical evidence linking aversive preterm and early-life SIDS events. Together with historical and anthropological evidence, our findings emphasize the necessity of cohort studies that consider these phenotypes with the aim of improving the identification of at-risk infants and reducing infant mortality.

RELEVANCE FOR PATIENTS

Preterm birth and neonatal circumcision are associated with a greater risk of SIDS, and efforts should be focused on reducing their rates.

Analysis of sudden infant death syndrome coverage in Canadian newspapers

Sudden infant death syndrome (SIDS; also known as crib death) describes the sudden unexpected death of an infant under one year of age, which remains unexplained after a thorough investigation. SIDS is a public health concern. It is the fourth leading cause of infant death in Canada. Newspapers are a major source of health information for the public, shape public perceptions and can direct the discussion around issues. Despite the potential influence of newspapers, no study has examined the portrayal of SIDS in Canadian newspapers over time. The purpose of our study was to gain an understanding of SIDS coverage in Canadian English language newspapers using the Canadian Newsstream database from 1970 to 2015 and the historical database: The Globe and Mail from 1844 to 1977. Generating descriptive quantitative and qualitative data, we noted a decline in SIDS coverage over time. Blame and misdiagnosis were two dominant themes in the coverage of SIDS with many other aspects around SIDS missing; for example, indigenous people, who are at higher risk for SIDS, were rarely mentioned. Our findings suggest problems in the content and frequency of coverage of SIDS that have the potential to shape the public understanding of SIDS.

Parent-infant co-sleeping and the implications for sudden infant death syndrome

In 2015 the National Institute for Health and Care Excellence (NICE) updated its 2006 guideline to clarify the association between parent infant co-sleeping and sudden infant death syndrome (SIDS). The practice of co-sleeping is a topic of continuing controversy and debate. Rather than highlighting the risks, the emphasis of the NICE guideline is to provide parents with balanced information so that they can make informed decisions about where their babies sleep. This contradicts previous public health messages on co-sleeping that discourages parents from the practice. Consequently, the updated national guideline has been criticised for failing to provide parents with safer sleep information, which has led to widespread confusion for parents and professionals. Health professionals can deliver safer sleep advice to support parents in their decision-making. However, as a result of inconsistent guidelines and evidence about parent-infant co-sleeping, health professionals may feel apprehensive and ill-equipped to provide advice and support. This article draws on a non-exhaustive literature review to discuss the risks and benefits of parent-infant co-sleeping, and the implications of this practice for SIDS. It also aims to provide transparency and improve understanding for health professionals so that they can support parents to adopt safer sleep strategies for their baby.

Synaptogenesis and Myelination in the Nucleus/Tractus Solitarius: Potential Role in Apnea of Prematurity, Congenital Central Hypoventilation, and Sudden Infant Death Syndrome

Fetuses as early as 15 weeks' gestation exhibit rhythmical respiratory movements shown by real-time ultrasonography. The nucleus/tractus solitarius is the principal brainstem respiratory center; other medullary nuclei also participate. The purpose was to determine temporal maturation of synaptogenesis. Delayed synaptic maturation may explain neurogenic apnea or hypoventilation of prematurity and some cases of sudden infant death syndrome. Sections of medulla oblongata were studied from 30 human fetal and neonatal brains 9 to 41 weeks' gestation. Synaptophysin demonstrated the immunocytochemical sequence of synaptogenesis. Other neuronal markers and myelin stain also were applied. The nucleus/tractus solitarius was similarly studied in fetuses with chromosomopathies, metabolic encephalopathies, and brain malformations. Synapse formation in the nucleus solitarius begins at about 12 weeks' gestation and matures by 15 weeks; myelination initiated at 33 weeks. Synaptogenesis was delayed in 3 fetuses with different conditions, but was not specific for only nucleus solitarius. Delayed synaptogenesis or myelination in the nucleus solitarius may play a role in neonatal hypoventilation, especially in preterm infants and in some sudden infant death syndrome cases.

Sudden infant death syndrome in an urban Aboriginal community

AIM

The study aims to understand sudden infant death syndrome (SIDS) risk and preventive practices in an urban Aboriginal community, through exploration of mothers' knowledge and practices and examination of coroner case records.

METHODS

Data were collected from the mothers of Aboriginal infants participating in the Gudaga Study, a longitudinal birth cohort study. At 2-3 weeks post-natal, mothers were asked about SIDS risk-reduction practices, infant sleeping position and smoking practices within the home. Questions were repeated when study infants were 6 months of age. During the first 18 months of the study, three infants within the cohort died. All deaths were identified as SIDS related. The Coroner reports for these infants were reviewed.

RESULTS

At the 2-3 weeks data collection point, approximately 66.2% (n = 98) of mothers correctly identified two or more SIDS risk-reduction strategies. At this same data point, approximately 82% (n = 122) of mothers were putting their infants to sleep on their backs (supine). Higher maternal education was significantly associated (P < 0.01), with identification of two or more correct SIDS risk-reduction strategies and supine sleeping position at 2-3 weeks. The Coroner considered two infants who had been sleeping in an unsafe sleeping environment.

CONCLUSION

Rates of SIDS deaths within the study community were much higher than the national average. Most mothers were putting their infant to sleep correctly even though they may be unaware that their practice was in accordance with recommended guidelines. Best practice safe sleeping environments are difficult to achieve for some families living in low socio-economic settings.

Sowing the seeds for a career in medicine: reflections and projections

Dr. George Lister delivered the following presentation as the Lee E. Farr Lecturer on May 8, 2011, which served as the culmination of the annual Student Research Day at Yale School of Medicine. He is the Chair of Pediatrics at the University of Texas Southwestern Medical School and Pediatrician-in-Chief at Children's Medical Center of Dallas. In his lecture to the medical students, who had just completed their research theses, Dr. Lister discusses his own work on sudden infant death syndrome (SIDS), demonstrating the complexity of clinical research and proving insight into the traits required of physician scientists. Committed to medical education and recognized by several awards for his mentorship, he ends the talk by imparting valuable advice on future physicians.

Research on and in medical education

Dr. George Lister of the University of Texas Southwestern Medical Center delivered the Lee E. Farr Lecture on Student Research Day on May 9, 2011. This day focused on the dissertation work of Yale School of Medicine MD students, whose research opportunities for prospective physicians were recently examined and critiqued by Yale's Committee to Promote Student Interest in Careers as Physician Scientists. Lister's talk served to highlight the importance of communication between the laboratory and the clinic in optimizing diagnostics and treatments, effectively affirming the validity of the Committee's objectives.