Sudden unexpected death in infancy in Denmark

Causes of sudden unexpected death in infants with and without pre-existing conditions: a retrospective autopsy study

OBJECTIVE

We investigated sudden unexpected death in infancy (SUDI) autopsy data from 1996 to 2015 inclusive, comparing findings from infants with and without pre-existing medical conditions.

DESIGN

Large, retrospective single-centre autopsy series.

SETTING

Tertiary paediatric hospital, London, UK.

METHODS

Non-identifiable autopsy findings were extracted from an existing research database for infants older than 7 days up to and including 365 days old who died suddenly and unexpectedly (SUDI; n=1739). Cases were classified into SUDI with pre-existing condition (SUDI-PEC) (n=233) versus SUDI without PEC (SUDI non-PEC) (n=929), where PEC indicates a potentially life-limiting pre-existing medical condition. Findings were compared between groups including evaluation of type of PEC and whether the deaths were medically explained (infectious or non-infectious) or apparently unexplained.

RESULTS

Median age of death was greater in SUDI-PEC compared with SUDI non-PEC (129 days vs 67 days) with similar male to female ratio (1.4:1). A greater proportion of deaths were classified as medically explained in SUDI-PEC versus SUDI non-PEC (73% vs 30%). Of the explained SUDI, a greater proportion of deaths were non-infectious for SUDI-PEC than SUDI non-PEC (66% vs 32%). SUDI-PEC (infectious) infants were most likely to have respiratory infection (64%), with susceptible PEC, including neurological, prematurity with a PEC, and syndromes or other anomalies.

CONCLUSION

SUDI-PEC deaths occur later in infancy and are likely to have their death attributed to their PEC, even in the absence of specific positive autopsy findings. Future research should aim to further define this cohort to help inform SUDI postmortem guidelines, paediatric clinical practice to reduce infant death, and to reduce the risk of overattribution of deaths in the context of a PEC.

Autopsy of all young sudden death cases is important to increase survival in family members left behind

Sudden cardiac death (SCD) is an important public health problem worldwide, accounting for an estimated 6-20% of total mortality. A significant proportion of SCD is caused by inherited heart disease, especially among the young. An autopsy is crucial to establish a diagnosis of inherited heart disease, allowing for subsequent identification of family members who require cardiac evaluation. Autopsy of cases of unexplained sudden death in the young is recommended by both the European Society of Cardiology and the American Heart Association. Overall autopsy rates, however, have been declining in many countries across the globe, and there is a lack of skilled trained pathologists able to carry out full autopsies. Recent studies show that not all cases of sudden death in the young are autopsied, likely due to financial, administrative, and organizational limitations as well as awareness among police, legal authorities, and physicians. Consequently, diagnoses of inherited heart disease are likely missed, along with the opportunity for treatment and prevention among surviving relatives. This article reviews the evidence for the role of autopsy in sudden death, how the cardiologist should interpret the autopsy-record, and how this can be integrated and implemented in clinical practice. Finally, we identify areas for future research along with potential for healthcare reform aimed at increasing autopsy awareness and ultimately reducing mortality from SCD.

Molecular autopsy: Twenty years of post-mortem diagnosis in sudden cardiac death

In the forensic medicine field, molecular autopsy is the post-mortem genetic analysis performed to attempt to unravel the cause of decease in cases remaining unexplained after a comprehensive forensic autopsy. This negative autopsy, classified as negative or non-conclusive, usually occurs in young population. In these cases, in which the cause of death is unascertained after a thorough autopsy, an underlying inherited arrhythmogenic syndrome is the main suspected cause of death. Next-generation sequencing allows a rapid and cost-effectives genetic analysis, identifying a rare variant classified as potentially pathogenic in up to 25% of sudden death cases in young population. The first symptom of an inherited arrhythmogenic disease may be a malignant arrhythmia, and even sudden death. Early identification of a pathogenic genetic alteration associated with an inherited arrhythmogenic syndrome may help to adopt preventive personalized measures to reduce risk of malignant arrhythmias and sudden death in the victim's relatives, at risk despite being asymptomatic. The current main challenge is a proper genetic interpretation of variants identified and useful clinical translation. The implications of this personalized translational medicine are multifaceted, requiring the dedication of a specialized team, including forensic scientists, pathologists, cardiologists, pediatric cardiologists, and geneticists.

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.

Epilepsy-Related Mortality in Children and Young Adults in Denmark: A Nationwide Cohort Study

BACKGROUND AND OBJECTIVES

Mortality is increased in epilepsy, but the important issue is that a proportion of epilepsy-related death is potentially preventable by optimized therapy and needs therefore to be identified. A new systematic classification of epilepsy-related mortality has been suggested by Devinsky et al. in 2016 to identify these preventable deaths. We applied this classification to an analysis of premature mortality in persons with epilepsy younger than 50 years.

METHODS

The study was a population-based retrospective cohort of all Danish citizens with and without epilepsy aged 1-49 years during 2007-2009. Information on all deaths was retrieved from the Danish Cause of Death Registry, autopsy reports, death certificates, and the Danish National Patient Registry. The primary cause of death in persons with epilepsy was evaluated independently by three neurologist, one neuro-pediatrician, and two cardiologists. In case of uncertainty a pathologist was consulted. All deaths were classified as either epilepsy- or not-epilepsy-related, and the underlying causes or modes of death were compared between persons with and without epilepsy.

RESULTS

During the study period 700 deaths were identified in persons with epilepsy, and 440 (62.9%) of these were epilepsy-related, hereof, 169 (38%) directly related to seizures and 181 (41%) due to an underlying neurological disease. SUDEP accounted for 80% of deaths directly related to epilepsy. Aspiration pneumonia was the cause of death in 80% of cases indirectly related to epilepsy.Compared with the background population, persons with epilepsy had a nearly four-fold increased all-cause mortality (adjusted mortality hazard ratio of 3.95 [95% CI 3.64-4.27], p<0.0001) and a higher risk of dying from various underlying causes including alcohol-related conditions (hazard ratio of 2.91 [95% CI 2.23-3.80], p<0.0001) and suicide (hazard ratio of 2.10 [95% CI 1.18-3.73], p=0.01).

DISCUSSION

The newly proposed classification for mortality in persons with epilepsy was useful in an unselected nationwide cohort. It helped classifying unnatural causes of death as epilepsy-related or not, and it helped identifying potentially preventable deaths. The leading causes of premature mortality in persons younger than 50 years were related to epilepsy and were thus potentially preventable by good seizure control.

Sudden cardiac death caused by myocarditis in persons aged 1-49 years: a nationwide study of 14 294 deaths in Denmark

Myocarditis is associated with an increased risk of sudden cardiac death (SCD) in the young. However, information on nationwide burden of SCD caused by myocarditis (SCD-myocarditis) is sparse. For this study all deaths among persons in Denmark aged 1–35 years in 2000–2009 and 36–49 years in 2007–2009 (27.1 million person-years) were included. Autopsy reports, death certificates, discharge summaries, and nationwide registries were used to identify all cases of SCD-myocarditis. In the 10-year study period, there were 14 294 deaths, of which we identified 1 363 (10%) SCD. Among autopsied SCD (n = 753, 55%), cause of death was myocarditis in 42 (6%) cases corresponding to an SCD-myocarditis incidence of 0.16 (95%CI: 0.11–0.21) per 100 000 person-years. Males had significantly higher incidence rates of SCD-myocarditis compared to females with an incidence rate ratio of 2.2 (95%CI: 1.1–4.1). Myocarditis was not registered as cause of death in any of the non-autopsied SCD (n = 610, 45%). In conclusion, after nationwide unselected inclusion of 14 294 deaths, we found that 6% of all autopsied SCD was caused by myocarditis. No cases of SCD-myocarditis were reported in the non-autopsied SCD, which could reflect underdiagnosing of myocarditis in non-autopsied SCD. Furthermore, our data suggest a female protection towards SCD-myocarditis.

Nationwide Study of Sudden Cardiac Death in People With Congenital Heart Defects Aged 0 to 35 Years

BACKGROUND

Congenital heart defects (CHD) are among the leading causes of sudden cardiac death (SCD) in the young. Nationwide incidence of SCD in people with CHD (SCD-CHD) has not been established in the young general population. The aims of this study were to investigate incidence of SCD-CHD and whether incidence of SCD-CHD in infants declined after implementation of nationwide fetal ultrasound screening in Denmark.

METHODS

All deaths (n=11 451) among people aged 0 to 35 years in Denmark in 2000 to 2009 (24.4 million person-years) were included. Danish death certificates, autopsy reports, records from hospitals and general practitioners, and data from nationwide Danish registries were used to identify SCD-CHD cases.

RESULTS

We identified 90 (11%) cases of SCD-CHD from 809 SCD. The incidence rate of SCD-CHD was 0.4 per 100 000 person-years among people aged 0 to 35 years. In total, 53 (59%) were diagnosed with CHD before death. Incidence of SCD was 9.6× higher among patients with CHD compared with people without CHD (P<0.01). Annual incidence of physical activity-related SCD-CHD among patients aged 2 to 35 years diagnosed with CHD was 0.9 per 100 000. The annual incidence rate of SCD-CHD in infants declined after implementation of nationwide fetal ultrasound screening (incidence rate ratio, 3.8; P<0.01).

CONCLUSIONS

The proportion of SCD-CHD in the young was 11%, which is higher than previously reported. Physical activity-related SCD-CHD was a rare event among patients with CHD. We observed an ≈4-fold lower incidence of SCD-CHD among infants born after implementation of nationwide screening.

Global trends in the extent of death scene investigation performed for sudden and unexpected death of infant (SUDI) cases: A systematic review

Sudden unexpected death of infants (SUDI) is the rapid and unexpected death of an infant aged less than 1year old. These deaths are referred for a medico-legal investigation to establish cause of death. National and regional protocols for the investigation of SUDI cases have been established in some countries and these typically include a death scene investigation component. However, there is a paucity of literature detailing the nature and extent of death scene investigation protocols. A systematic review was conducted to review the scope of death scene investigation of SUDI cases worldwide. Relevant articles (n=74) were identified by searching four literature databases, three discipline-specific journals, as well as each article's reference list, until saturation was reached. Of the 16 countries represented by the included articles, seven made specific reference to the standardised protocol used, which included photography, interviews and/or scene re-enactments. The remaining 54 studies appeared to include a subset of these analyses during death scene investigation, which varied between countries, and between SUDI admissions. This may be attributed to the differing socio-economic standings of countries, and the resources available. Only four studies were from developing countries, three of which originated from South Africa. Overall, where a standardised death scene investigation was performed, it added value to the post-mortem investigation; as such, death scene investigation should be encouraged in SUDI investigation. To this end, protocols should be established nationally, and contain core analyses, which could be expanded depending on the needs and resources of the country.

Sudden infant death "syndrome"-Insights and future directions from a Utah population database analysis

"Sudden Infant Death syndrome" (SIDS) represents the commonest category of infant death after the first month of life. As genome scale sequencing greatly facilitates the identification of new candidate disease variants, the challenges of ascribing causation to these variants persists. In order to determine the extent to which SIDS occurs in related individuals and their pedigree structure we undertook an analysis of SIDS using the Utah Population Database, recording, for example, evidence of enrichment for genetic causation following the back-to-sleep recommendations of 1992 and 1994. Our evaluation of the pre- and post back-to-sleep incidence of SIDS in Utah showed a decrease in SIDS incidence on the order of eightfold following back-to-sleep. An odds ratio of 4.2 for SIDS recurrence among sibs was identified from 1968 to 2013 which was similar to the odds ratio of 4.84 for death due to other or unknown cause among sibs of SIDS cases for the same time period. Combining first through thid degree relatives yielded an odds ratio of SIDS recurrence of 9.29 in the post-back-to-sleep (1995-2013) subset of SIDS cases where similar calculations of first-third degree relatives for the entire time period of 1968-2013 showed an odds ratio of 2.95. Expanded multigenertional pedigrees showing enrichment for SIDS were also identified. Based on these findings we hypothesize that post back-to-sleep SIDS, especially recurrences within a family, are potentially enriched for genetic causes due to the impact of safe sleeping guidelines in mitigating environmental risk factors. © 2016 Wiley Periodicals, Inc.

Genetic investigations of sudden unexpected deaths in infancy using next-generation sequencing of 100 genes associated with cardiac diseases

Sudden infant death syndrome (SIDS) is the most frequent manner of post-perinatal death among infants. One of the suggested causes of the syndrome is inherited cardiac diseases, mainly channelopathies, that can trigger arrhythmias and sudden death. The purpose of this study was to investigate cases of sudden unexpected death in infancy (SUDI) for potential causative variants in 100 cardiac-associated genes. We investigated 47 SUDI cases of which 38 had previously been screened for variants in RYR2, KCNQ1, KCNH2 and SCN5A. Using the Haloplex Target Enrichment System (Agilent) and next-generation sequencing (NGS), the coding regions of 100 genes associated with inherited channelopathies and cardiomyopathies were captured and sequenced on the Illumina MiSeq platform. Sixteen (34%) of the SUDI cases had variants with likely functional effects, based on conservation, computational prediction and allele frequency, in one or more of the genes screened. The possible effects of the variants were not verified with family or functional studies. Eight (17%) of the SUDI cases had variants in genes affecting ion channel functions. The remaining eight cases had variants in genes associated with cardiomyopathies. In total, one third of the SUDI victims in a forensic setting had variants with likely functional effect that presumably contributed to the cause of death. The results support the assumption that channelopathies are important causes of SUDI. Thus, analysis of genes associated with cardiac diseases in SUDI victims is important in the forensic setting and a valuable supplement to the clinical investigation in all cases of sudden death.

Impact of smoke-free legislation on perinatal and infant mortality: a national quasi-experimental study

Smoke-free legislation is associated with improved early-life outcomes; however its impact on perinatal survival is unclear. We linked individual-level data with death certificates for all registered singletons births in England (1995–2011). We used interrupted time series logistic regression analysis to study changes in key adverse perinatal events following the July 2007 national, comprehensive smoke-free legislation. We studied 52,163 stillbirths and 10,238,950 live-births. Smoke-free legislation was associated with an immediate 7.8% (95%CI 3.5–11.8; p < 0.001) reduction in stillbirth, a 3.9% (95%CI 2.6–5.1; p < 0.001) reduction in low birth weight, and a 7.6% (95%CI 3.4–11.7; p = 0.001) reduction in neonatal mortality. No significant impact on SIDS was observed. Using a counterfactual scenario, we estimated that in the first four years following smoke-free legislation, 991 stillbirths, 5,470 cases of low birth weight, and 430 neonatal deaths were prevented. In conclusion, smoke-free legislation in England was associated with clinically important reductions in severe adverse perinatal outcomes.

Tobacco Control Policies and Sudden Infant Death Syndrome in Developed Nations

This paper estimates the effects of higher cigarette prices and smoke-free policies on the prevalence of Sudden Infant Death Syndrome (SIDS). Using a panel of developed countries over a 20 year period, we find that higher cigarette prices are associated with reductions in the prevalence of SIDS. However, we find no evidence that smoke-free policies are associated with declines in SIDS.

Sudden infant death syndrome in Korea: a retrospective analysis of autopsy-diagnosed cases

This study aimed to elucidate the demographic and sleeping environmental factors associated with sudden infant death syndrome (SIDS) in Korea. The autopsy reports of all SIDS cases reported to the National Forensic Service and Seoul National University College of Medicine between 1996 and 2008 were reviewed for data collection and analysis to identify the risk factors for SIDS. Analysis of the 355 SIDS cases reported within the study period revealed that of the 168 (47.3%) cases for which sleeping position before death had been reported, 75 (44.7%) cases had occurred after placement in prone or side position. Of the 204 (57.5%) cases for which bed-sharing situation had been reported, 121 (59.3%) deaths had occurred during bed-sharing, of which 54 (44.6%) infants were under 3 months of age, a significantly younger age than that of the non-bed-sharing cases (P = 0.0279). Analysis of the results indicated no tendency toward an increase or decrease in the use of a prone or side position. Rather, there was a statistically significant increasing trend for bed-sharing over the study period (OR, 1.087; 95% CI, 1.004-1.177; P = 0.04). These findings indicate the need for nationwide educational programs promoting a safe sleeping environment to enhance SIDS prevention.

Sudden death in the first 2 years of life following immunization in the Republic of Korea

BACKGROUND

Because the peak age for incidence of sudden deaths in infancy temporally coincides with the age of infant primary immunization, some have raised the question as to whether immunization is a risk factor for sudden death in infancy. Recent occurrence of two sudden deaths in infants in Korea has renewed concerns about the causal association between immunization and sudden deaths in infants.

METHODS

We carried out a retrospective review of data from the Korea Centers for Disease Control and Prevention Adverse Events Following Immunization Surveillance System and Vaccine Compensation programs.

RESULTS

From 1994 to 2011, a total of 45 cases of sudden deaths in the first 2 years of life following immunization were reported in Korea. The causes of death were classified as follows: infectious diseases (n= 13); accidental injuries (n= 7); congenital abnormalities (n= 2); and malignancy (n= 1). Of 20 sudden deaths in infancy, nine deaths met Brighton Collaboration case definition level I and II, and therefore were classified as possible sudden infant death syndrome cases. Hepatitis B vaccine (n= 13) was the most frequent vaccine with temporal association with sudden deaths in the first 2 years of life.

CONCLUSION

Few sudden deaths in the first 2 years of life following immunization have been reported, despite the use of universal immunization in Korea. The majority of deaths in infancy did not meet case definition for sudden infant death syndrome. Encouraging investigators to perform thorough investigation, including postmortem autopsy and death scene examination, may promote data comparability and provide guidance on decision-making in the vaccine-safety monitoring and response system in Korea.

The prevalence of mutations in KCNQ1, KCNH2, and SCN5A in an unselected national cohort of young sudden unexplained death cases

INTRODUCTION

Sudden unexplained death account for one-third of all sudden natural deaths in the young (1-35 years). Hitherto, the prevalence of genopositive cases has primarily been based on deceased persons referred for postmortem genetic testing. These deaths potentially may represent the worst of cases, thus possibly overestimating the prevalence of potentially disease causing mutations in the 3 major long-QT syndrome (LQTS) genes in the general population. We therefore wanted to investigate the prevalence of mutations in an unselected population of sudden unexplained deaths in a nationwide setting.

METHODS

DNA for genetic testing was available for 44 cases of sudden unexplained death in Denmark in the period 2000-2006 (equaling 33% of all cases of sudden unexplained death in the age group). KCNQ1, KCNH2, and SCN5A were sequenced and in vitro electrophysiological studies were performed on novel mutations.

RESULTS

In total, 5 of 44 cases (11%) carried a mutation in 1 of the 3 genes corresponding to 11% of all investigated cases (R190W KCNQ1, F29L KCNH2 (2 cases), P297S KCNH2 and P1177L SCN5A). P1177L SCN5A has not been reported before. In vitro electrophysiological studies of P1177L SCN5A revealed an increased sustained current suggesting a LQTS phenotype.

CONCLUSION

In a nationwide setting, the genetic investigation of an unselected population of sudden unexplained death cases aged 1-35 years finds a lower than expected number of mutations compared to referred populations previously reported. We therefore conclude that the prevalence of mutations in the 3 major LQTS associated genes may not be as abundant as previously estimated.

Cardiac channelopathies and sudden infant death syndrome

Sudden infant death syndrome (SIDS) is always a devastating and unexpected occurrence. SIDS is the leading cause of death in the first 6 months after birth in the industrialized world. Since the discovery in 1998 of long QT syndrome as an underlying substrate for SIDS, around 10-20% of SIDS cases have been proposed as being caused by genetic variants in either ion channel or ion channel-associated proteins. Until now, 10 cardiac channelopathy susceptibility genes have been found to be implicated in the pathogenesis of SIDS. Four of the genes encode cardiac ion channel α-subunits, 3 genes encode ion channel β-subunits, and 3 genes encode other channel-interacting proteins. All 10 genes have been associated with primary electrical heart diseases. SIDS may hereby be the initial symptom of rare primary electric channelopathies such as long QT, short QT and Brugada syndrome, as well as catecholaminergic polymorphic ventricular tachycardia. In this review we describe the functional role of sodium, potassium and calcium channels in propagation, depolarization and repolarization in the context of the 4 arrhythmogenic diseases reported to be associated with SIDS. Lastly, the possibility of postmortem genetic testing and potential recommendations on how to deal with family members are discussed.