Evolution and significance of the triple risk model in sudden infant death syndrome

Enigmatic thymus: Variations in anatomical localisation of thymic tissue as an easily misdiagnosed congenital anomaly in surgical practice

We point out the issue of differential diagnosis regarding the finding of ectopically localised thymic tissue (a thymic cyst) in the neck. Thymic tissue can be found anywhere along its developmental tract of descent, from the angle of the mandible to the upper mediastinum. Disruption of the thymic descent can result in ectopically/abnormally localised islets of accessory thymic tissue, which may undergo cystic changes, as described in a case report by Sun et al. This anatomical variation of the thymus may be clinically misinterpreted as a neoplasm or other congenital anomalies as a branchial cyst, lymphatic malformation or cystic hygroma. The present editorial focuses on the challenge of establishing a diagnosis of ectopically localised tissue of thymus often presented as a lateral cervical mass, especially in the case of cystic variation/degeneration of this thymic tissue. We summarise hypotheses on the origin of such congenital cervical thymic cysts from the point of view of evolutionary history and embryology. We also discuss lesser-known facts about the anatomy, histopathology and developmental biology of the thymus as one of the most enigmatic organs in the human body.

The global burden of disease attributable to preterm birth and low birth weight in 204 countries and territories from 1990 to 2019: An analysis of the Global Burden of Disease Study

Background

Preterm birth and low birth weight (PBLBW), recognised globally as primary contributors to infant mortality in children under five, have not been sufficiently investigated in terms of their worldwide impact. In this study we aimed to thoroughly evaluate the contemporary trends in disease burden attributable to PBLBW.

Methods

We analysed data from 204 countries and territories between 1990-2019, as sourced from the 2019 Global Burden of Disease Study. We analysed the global incidence of mortality and disability-adjusted life years (DALYs) associated with PBLBW, stratified by age, gender, year, and geographic location, alongside the socio-demographic index (SDI). We calculated the annual percentage changes to evaluate the dynamic trends over time. We employed a generalised linear model and scrutinised the relationship between the SDI and the disease burden attributed to PBLBW.

Results

In 2019, the global age-standardised rate of deaths and DALYs related to PBLBW showed significant declines. Over the period 1990-2019, both death and DALY rates displayed substantial downward trends, with similar change trends observed for both females and males. Age-specific ratios revealed a decrease in PBLBW-related deaths and DALYs with increasing age, primarily during the neonatal stages (zero to 27 days). The leading three causes of PBLBW-related DALYs in 2019 were neonatal disorders, lower respiratory infections, and sudden infant death syndrome. Furthermore, the association between SDI and PBLBW-related DALYs indicated that the age-standardised DALY rates in 204 countries and territories worldwide were negatively correlated with SDI in 2019. From 1990 to 2019, the age-standardised DALY rates decreased linearly in most regions, except sub-Saharan Africa.

Conclusions

The persistent global burden of disease associated with PBLBW is particularly pronounced in neonates aged less than 28 days and in regions with low SDI. In this study, we highlighted the critical need for tailored interventions aimed at mitigating the detrimental effects of PBLBW to attain specific sustainable development goals, particularly those centred on enhancing child survival and overall well-being.

Prenatal and postnatal factors associated with sudden infant death syndrome: an umbrella review of meta-analyses

BACKGROUND

Comprehensive quantitative evidence on the risk and protective factors for sudden infant death syndrome (SIDS) effects is lacking. We investigated the risk and protective factors related to SIDS.

METHODS

We conducted an umbrella review of meta-analyses of observational and interventional studies assessing SIDS-related factors. PubMed/MEDLINE, Embase, EBSCO, and Google Scholar were searched from inception until January 18, 2023. Data extraction, quality assessment, and certainty of evidence were assessed by using A Measurement Tool Assessment Systematic Reviews 2 following PRISMA guidelines. According to observational evidence, credibility was graded and classified by class and quality of evidence (CE; convincing, highly suggestive, suggestive, weak, or not significant). Our study protocol was registered with PROSPERO (CRD42023458696). The risk and protective factors related to SIDS are presented as equivalent odds ratios (eORs).

RESULTS

We identified eight original meta-analyses, including 152 original articles, covering 12 unique risk and protective factors for SIDS across 21 countries/regions and five continents. Several risk factors, including prenatal drug exposure [eOR = 7.84 (95% CI = 4.81-12.79), CE = highly suggestive], prenatal opioid exposure [9.55 (95% CI = 4.87-18.72), CE = suggestive], prenatal methadone exposure [9.52 (95% CI = 3.34-27.10), CE = weak], prenatal cocaine exposure [4.38 (95% CI = 1.95-9.86), CE = weak], prenatal maternal smoking [2.25 (95% CI = 1.95-2.60), CE = highly suggestive], postnatal maternal smoking [1.97 (95% CI = 1.75-2.22), CE = weak], bed sharing [2.89 (95% CI = 1.81-4.60), CE = weak], and infants found with heads covered by bedclothes after last sleep [11.01 (95% CI = 5.40-22.45), CE = suggestive], were identified. On the other hand, three protective factors, namely, breastfeeding [0.57 (95% CI = 0.39-0.83), CE = non-significant], supine sleeping position [0.48 (95% CI = 0.37-0.63), CE = suggestive], and pacifier use [0.44 (95% CI = 0.30-0.65), CE = weak], were also identified.

CONCLUSIONS

Based on the evidence, we propose several risk and protective factors for SIDS. This study suggests the need for further studies on SIDS-related factors supported by weak credibility, no association, or a lack of adequate research.

Infant Mortality Trends and Determinants in Kazakhstan

Infant mortality rate (IMR) is a crucial indicator of healthcare performance and a reflection of a country's socioeconomic development. We analyzed the trends of IMR in Central Asia (CA) countries and its determinants in Kazakhstan, which is a middle-income country. Linear regression was used for IMR trend analysis in CA countries from 2000 to 2020 and for exploring associations between IMR and socioeconomic factors, health service-related factors, and population health indicators-related factors. A gamma generalized linear model was applied to define associations with various determinants. Our analysis revealed that IMR has decreased in all CA countries, with Kazakhstan having the lowest rate in 2000 and 2020. Our results suggest that socioeconomic indicators, such as total unemployment, Gini index, current health expenditure, gross domestic product (GDP), proportion of people living in poverty, and births by 15-19-year-old mothers, were associated with increased infant mortality rates. Improving socioeconomic conditions, investing in healthcare systems, reducing poverty and income inequality, and improving access to education, are all potential issues for further development. Addressing these factors may be critical for improving maternal and child health outcomes in the region.

Risk of Sudden Infant Death Syndrome Among Siblings of Children Who Died of Sudden Infant Death Syndrome in Denmark

IMPORTANCE

Sudden infant death syndrome (SIDS) remains a leading cause of death during the first year of life. The etiology of SIDS is complex and remains largely unknown.

OBJECTIVE

To evaluate whether siblings of children who died of SIDS have a higher risk of SIDS compared with the general pediatric population.

DESIGN, SETTING, AND PARTICIPANTS

This register-based cohort study used Danish nationwide registers. Participants were all infants (<1 year) in Denmark between January 1, 1978, and December 31, 2016, including siblings of children who died of SIDS. Siblings were followed up from the index cases' date of SIDS, date of birth, or immigration, whichever came first, and until age 1 year, emigration, developing SIDS, death, or study end. The median (IQR) follow-up was 1 (1-1) year. Data analysis was conducted from January 2017 to October 2022.

MAIN OUTCOMES AND MEASURES

Standardized incidence ratios (SIRs) of SIDS were calculated with Poisson regression models relative to the general population.

RESULTS

In a population of 2 666 834 consecutive births (1 395 199 [52%] male), 1540 infants died of SIDS (median [IQR] age at SIDS, 3 [2-4] months) during a 39-year study period. A total of 2384 younger siblings (cases) to index cases (first sibling with SIDS) were identified. A higher rate of SIDS was observed among siblings compared with the general population, with SIRs of 4.27 (95% CI, 2.13-8.53) after adjustment for sex, age, and calendar year and of 3.50 (95% CI, 1.75-7.01) after further adjustment for mother's age (<29 years vs ≥29 years) and education (high school vs after high school).

CONCLUSIONS AND RELEVANCE

In this nationwide study, having a sibling who died of SIDS was associated with a 4-fold higher risk of SIDS compared with the general population. Shared genetic and/or environmental factors may contribute to the observed clustering of SIDS. The family history of SIDS should be considered when assessing SIDS risk in clinical settings. A multidisciplinary genetic evaluation of families with SIDS could provide additional evidence.

Protecting Infants from Sudden Unexpected Infant Death: Guidelines for Interventions during the Perinatal Period from the French National College of Midwives

With 300-400 annual deaths in France, sudden unexpected infant death (SUID) is the leading cause of mortality in France among infants from the end of their first through their 12th month of life. These clinical practice guidelines aim to identify strategies for (future) parents to prevent avoidable SUIDs. They are based on a narrative literature review and an analysis of the existing reports and guidelines available on the topic in 2019-2020. In summary, it is recommended that parents ensure that their infants sleep on their back on a firm, empty surface in a sufficiently ventilated environment, share the parental bedroom, and be breastfed and vaccinated. All of these actions create protective factors against SUID. Conversely, parents should know that several factors increase the risk of SUID: unsafe sleep, maternal smoking, passive smoking after birth, exposure to alcohol or other psychoactive substances, and excessive heat. Precis: Sudden Unexpected Infant Death prevention includes infants being breastfed and vaccinated, sleeping on their back, on a firm, empty surface, near parents, and that they are not overheated.

The Science (or Nonscience) of Research Into Sudden Infant Death Syndrome (SIDS)

This Viewpoint paper presents a timely and constructive critique of mainstream SIDS research. It is concerning that twenty-first century medical science has not provided an answer to the tragic enigma of SIDS. The paper helps explain why this is so and illustrates possible shortcomings in the investigation of Sudden Infant Death Syndrome/Sudden Unexplained Infant Death (SIDS/SUID) by mainstream researchers. Mainstream findings are often based on questionable and dogmatic assumptions that return to founding notions such as the Triple Risk Hypothesis and the contention that the mechanisms underlying SIDS/SUID are heterogeneous in nature. The paper illustrates how the pathological findings in SIDS have been under-investigated (or ignored) and that key epidemiological risk factors have slipped from memory. This apparent amnesia has resulted in failure to use these established SIDS facts to substantiate the significance of various neuropathological, neurochemical, or other research findings. These unsupported findings and their derivative hypotheses are therefore ill-founded and lack scientific rigor.

CONCLUSION

The deficits of SIDS "science" revealed in this paper explain why the SIDS enigma has not yet been solved. To make progress in understanding SIDS, it is important that researchers, as scientists, uphold standards of research. Encouragement for new directions of research is offered.

Sudden unexpected death in infancy: Severe pulmonary anatomopathological findings in spite of inconsistent clinical features

Respiratory tract infections play a considerable pathogenetic role in many cases of sudden infant death (SID). Frequently, clinicians encounter difficulties in diagnosing the disease because of its often unspecific clinical and radiological presentation. We report three cases of sudden unexpected death in infancy (SUDI), involving two males and one female admitted to hospital due to mild respiratory distress. In all three cases, complete post-mortem investigations were successful in uncovering interstitial lung disease as the cause of death. These cases highlight the key role of infection-related interstitial lung diseases in the pathogenesis of some currently unexplained SUDI/SIDS and the diagnostic difficulties due to the variable clinical and histological pattern, thereby explaining the importance of performing complete post-mortem investigations whenever an infant dies suddenly and unexpectedly.

Feasibility and Acceptability of a Tailored Infant Safe Sleep Coaching Intervention for African American Families

Background: Approximately 3600 infants die suddenly and unexpectedly annually in the United States. Research suggests limitations of current behavioral interventions to reduce the risk for sleep-related deaths among African American families living in under-resourced neighborhoods. Guided by the theory of planned behavior and the socio-ecological model, the My Baby’s Sleep (MBS) intervention intends to reduce the risk for sleep-related infant deaths while addressing complex needs of African American families living in under-resourced neighborhoods. Objective: To assess feasibility and acceptability of MBS, a 7-month intervention that includes four home visits and multiple check-ins via phone and text message. Methods: This was a single-arm feasibility and acceptability study with quantitative and qualitive measures. African American families were recruited from community agencies that served an under-resourced metropolitan area. Results: Eight families (eight mothers, nine co-caregivers) completed the intervention. Families reported high acceptability of MBS content, process, and format, as evidenced by qualitative data and mean evaluation scores. Conclusion: MBS is feasible and acceptable among African American families living in under-resourced neighborhoods. These results suggest further investigation of MBS intervention efficacy in a large-scale randomized controlled trial.

Socioeconomic Effects in Cyberbullying: Global Research Trends in the Educational Context

Nowadays, cyberbullying has become a problem of social harassment in numerous educational centres worldwide. New communication technologies have provided the perfect support for the development of this type of harassment in peer relationships, in addition to being linked to broad social and economic circumstances. In this study, the global trends of the socioeconomic implications of cyberbullying in the educational context have been analysed, from 2004 to 2019. Thus, a bibliometric analysis has been applied to 1128 articles, obtaining results of the evolution of scientific activity in this period. The articles are mainly associated with the thematic areas of Social Sciences, Psychology, Medicine and Computer Science. Seven main thematic axes have been detected, highlighting those related to the psychological aspect, adolescence, and the school environment. Likewise, the link of the main authors, institutions, and countries to these lines of research has been detected. The evidence has shown the interest and relevance of this topic at the international level. Future research lines propose different analyses about how certain socioeconomic factors influence this psychological harassment inside and outside the classroom.

Knowledge assessment of sudden infant death syndrome risk factors in expectant mothers: A prospective monocentric descriptive study

In France, approximately 500 deaths per year are related to sudden infant death syndrome (SIDS). After a 75% reduction of SIDS-related deaths in the 1990s, thanks to large prevention campaigns directing parents to put their infants to sleep on their back, the number of SIDS-related deaths remains stable. However, we estimate that 100-200 infant deaths per year in France could be prevented with better education on the risk factors for SIDS. In this prospective, descriptive monocentric study, we aimed to evaluate the level of expectant women's knowledge about SIDS. Questionnaires were distributed during a midwife consultation. A score on sleeping conditions, environmental and protective factors was determined with coefficients attributed according to their relevance to SIDS. Of 296 questionnaires distributed, 202 were completed and included in the analysis from March 1 to September 21, 2018. Scores were distributed from 2 to 46/50. The average score was 28.6/50. Information was principally obtained from media and not health professionals. When the information was delivered by a caregiver, in particular by a paediatrician, we observed better knowledge among these women. This study shows that it is important for health professionals to take the time to inform future mothers about the risk factors for SIDS, especially the least informed population groups such as young mothers and those from lower socioeconomic status, in order to reduce the number of avoidable infant deaths.

Sudden Unexpected Infant Death: Review and Analysis of Adherence to Recommendations

Introduction Sudden Unexpected Infant Death (SUID) is a term that englobes the sudden and unexpected death of an infant less than 12 months, which can be explained by organic or traumatic causes, or that can't be explained such as cases of Sudden Infant Death Syndrome (SIDS). Although many risk factors have been associated with this syndrome, one of the most widely associated and studied are incorrect sleeping techniques and practices. In 2016, the American Academy of Pediatrics (AAP) updated their safe-sleeping guidelines and sleeping environment recommendations and strategies to prevent SIDS. Methods We conducted a cross-sectional study to analyze the sleeping environments in infants that attended both the inpatient and outpatient services at a public pediatric hospital in Mexico City. A 6-item questionnaire was applied to the parent or guardian to assess the sleeping habits of infants in their homes. Results A total of 184 infants were included in the study, with a mean age of 5.87 months. Overall, the number of parents that follow safe sleeping practices was very low, with no parents following all the AAP recommendations, and over 10% not following any. Although there is uncertainty about the pathogenesis of this syndrome, the focus has shifted to prevention, especially regarding the modifiable risk factors. Conclusions It was demonstrated that our population did not know about the proper and safe sleeping techniques. In the nearby future, our goal is for health authorities in our country to implement a strategy to make the AAP recommendations part of government health campaigns.

Sudden Unexpected Death and the Mammalian Dive Response: Catastrophic Failure of a Complex Tightly Coupled System

In tightly coupled complex systems, when two or more factors or events interact in unanticipated ways, catastrophic failures of high-risk technical systems happen rarely, but quickly. Safety features are commonly built into complex systems to avoid disasters but are often part of the problem. The human body may be considered as a complex tightly coupled system at risk of rare catastrophic failure (sudden unexpected death, SUD) when certain factors or events interact. The mammalian dive response (MDR) is a built-in safety feature of the body that normally conserves oxygen during acute hypoxia. Activation of the MDR is the final pathway to sudden cardiac (SCD) in some cases of sudden infant death syndrome (SIDS), sudden unexpected death in epilepsy (SUDEP), and sudden cardiac death in water (SCDIW, fatal drowning). There is no single cause in any of these death scenarios, but an array of, unanticipated, often unknown, factors or events that activate or interact with the mammalian dive reflex. In any particular case, the relevant risk factors or events might include a combination of genetic, developmental, metabolic, disease, environmental, or operational influences. Determination of a single cause in any of these death scenarios is unlikely. The common thread among these seemingly different death scenarios is activation of the mammalian dive response. The human body is a complex tightly coupled system at risk of rare catastrophic failure when that "safety feature" is activated.

Sudden unexpected postnatal collapse

This review of Sudden Unexpected Postnatal Collapse (SUPC) highlights the challenges in definition and nomenclature that currently exist. In comparing SUPC with Sudden Unexpected Death in Infancy (SUDI), the potentially avoidable nature of many SUPC is emphasised and the role of positioning and public awareness explored. The article focusses on the implementation of preventative strategies in the immediate postnatal period and the role of therapeutic hypothermia in ameliorating long term neurological injury.

Neuropathological Developments in Sudden Infant Death Syndrome

A wide variety of neuropathological abnormalities have been investigated in infants who have died of sudden infant death syndrome (SIDS). Issues which detracted from early studies included failure to use uniform definitions of SIDS and lack of appropriately matched control populations. Development of the triple risk model focused attention on the concept of an inherent susceptibility to unexpected death in certain infants, with research demonstrating a role for the neurotransmitter serotonin within the brainstem. However, it now appears that neuropathological abnormalities in SIDS infants are more complex than a simple serotonergic deficiency in certain medullary nuclei but instead could involve failure of an integrated network of neurochemical transmitters in a variety of subcortical locations. The following overview examines recent research developments looking particularly at the potential role of the peptide neurotransmitter substance P and its neurokinin-1 receptor in multiple nuclei within the brainstem, asymmetry and microdysgenesis of the hippocampus, and decreased orexin levels within dorsomedial, perifornical, and lateral levels in the hypothalamus. Whether such research will lead to identifiable biomarker for infants at risk of SIDS is yet to be established. Use of standardized and consistent methods of classifying and categorizing infant deaths will be pivotal in generating reproducible research results.

Dysfunction of NaV1.4, a skeletal muscle voltage-gated sodium channel, in sudden infant death syndrome: a case-control study

BACKGROUND

Sudden infant death syndrome (SIDS) is the leading cause of post-neonatal infant death in high-income countries. Central respiratory system dysfunction seems to contribute to these deaths. Excitation that drives contraction of skeletal respiratory muscles is controlled by the sodium channel NaV1.4, which is encoded by the gene SCN4A. Variants in NaV1.4 that directly alter skeletal muscle excitability can cause myotonia, periodic paralysis, congenital myopathy, and myasthenic syndrome. SCN4A variants have also been found in infants with life-threatening apnoea and laryngospasm. We therefore hypothesised that rare, functionally disruptive SCN4A variants might be over-represented in infants who died from SIDS.

METHODS

We did a case-control study, including two consecutive cohorts that included 278 SIDS cases of European ancestry and 729 ethnically matched controls without a history of cardiovascular, respiratory, or neurological disease. We compared the frequency of rare variants in SCN4A between groups (minor allele frequency <0·00005 in the Exome Aggregation Consortium). We assessed biophysical characterisation of the variant channels using a heterologous expression system.

FINDINGS

Four (1·4%) of the 278 infants in the SIDS cohort had a rare functionally disruptive SCN4A variant compared with none (0%) of 729 ethnically matched controls (p=0·0057).

INTERPRETATION

Rare SCN4A variants that directly alter NaV1.4 function occur in infants who had died from SIDS. These variants are predicted to significantly alter muscle membrane excitability and compromise respiratory and laryngeal function. These findings indicate that dysfunction of muscle sodium channels is a potentially modifiable risk factor in a subset of infant sudden deaths.

FUNDING

UK Medical Research Council, the Wellcome Trust, National Institute for Health Research, the British Heart Foundation, Biotronik, Cardiac Risk in the Young, Higher Education Funding Council for England, Dravet Syndrome UK, the Epilepsy Society, the Eunice Kennedy Shriver National Institute of Child Health & Human Development of the National Institutes of Health, and the Mayo Clinic Windland Smith Rice Comprehensive Sudden Cardiac Death Program.

Why is a prone sleeping position dangerous for certain infants?

The prone (face down) sleeping position is known to be associated with a significantly increased risk of sudden and unexpected death in infancy (sudden infant death syndrome or SIDS), however, the reasons for this are unclear. Suggested mechanisms have involved suffocation from occlusion of the external airways by soft bedding/pillows or from flattening of the nose with backward displacement of the tongue, rebreathing of carbon dioxide, blunting of arousal responses with decreased cardiac responses to auditory stimulation, diaphragmatic splinting or fatigue, lowering of vasomotor tone with tachycardia, nasopharyngeal bacterial overgrowth, overheating, alteration of sleep patterns, compromise of cerebral blood flow and upper airway obstruction from distortion of nasal cartilages. Recent studies have, however, shown a significant reduction in substance P in the inferior portion of the olivo-cerebellar complex in SIDS infants which is crucial for the integration of motor and sensory information for the control of head and neck movement. This deficit may explain why some infants are not able to move their faces away from potentially dangerous sleeping environments.