What is the mechanism of SIDS? Clues from epidemiology

Regional variation in sudden unexpected death in infancy in New Zealand

AIM

To estimate the relative risk of sudden unexpected death in infancy (SUDI) by district health board (DHB) in New Zealand after adjustment for socio-economic deprivation, ethnicity and other demographic factors.

METHODS

We conducted a population-based cohort study using data from the Integrated Data Infrastructure, a large research database containing linked data from a range of government agencies. The study population was all live births and their mothers in New Zealand from 2012 to 2018. The exposure of interest was DHB. The outcome was SUDI.

RESULTS

There were 418 068 live births in New Zealand from 2012 to 2018, and of these 415 401 (99.4%) had valid DHB data. There was considerable variation in the proportion of infants in each DHB living in the most deprived decile varying from 4.5% in Nelson, West Coast and Canterbury to 29.7% in Counties Manukau. There were 267 SUDI cases, giving an overall rate of 0.64/1000 live births during the study period (2012-2018). The SUDI rate varied from 1.11/1000 in Northland to 0.30/1000 in Waitemata and Auckland. Counties Manukau had the largest number of deaths (n = 54; rate = 1.08/1000). Five DHB regions had increased risk of SUDI compared to the reference group but, after adjustment, no DHB was significantly increased.

CONCLUSIONS

This study found that there is marked variation in SUDI risk by DHB, but this is explained by socio-economic and demographic variation within DHBs. This study emphasises the importance of the contribution of social determinants of health to SUDI.

Sudden Unexpected Death in Infancy [SUDI]: What the clinician, pathologist, coroner and researchers want to know

The loss of an apparently healthy infant is confronting for any family, puzzling for a clinician and challenging for the pathologist charged with the task of demonstrating a cause for death. The term "cot death" evolved to "sudden infant death syndrome" [SIDS] and now "sudden unexpected death in infancy [SUDI]" as the epidemiology and pathology of infant death changed. Community interventions were successful in changing sleep practices for young babies. The current research focus is on understanding genetic predispositions to unexpected death in early childhood. Whilst much has been achieved in reducing the infant mortality rate from SUDI by between 50%, and 80% in some countries, over the last 30 years, there remain challenges for improving rates of accurate diagnosis and reaching out to more vulnerable families with clearly modifiable risk factors for SUDI. These challenges directly involve the clinician through taking a systematic and detailed history and better standardised death scene evaluations with specifically accredited assessors. Better knowledge regarding circumstances of SUDI cases will help Coroners and researchers provide answers for grieving families now, and in the future contribute to further reductions in the rate of SUDI in communities across the world.

Sudden infant death syndrome: Melatonin, serotonin, and CD34 factor as possible diagnostic markers and prophylactic targets

Sudden infant death syndrome (SIDS) is one of the primary causes of death of infants in the first year of life. According to the WHO's data, the global infant mortality rate is 0.64-2 per 1,000 live-born children. Molecular and cellular aspects of SIDS development have not been identified so far. The purpose of this paper is to verify and analyze the expression of melatonin 1 and 2 receptors, serotonin (as a melatonin precursor), and CD34 molecules (as hematopoietic and endothelial markers of cardiovascular damage) in the medulla, heart, and aorta in infants who died from SIDS. An immunohistochemical method was used to investigate samples of medulla, heart, and aorta tissues of infants 3 to 9 months of age who died from SIDS. The control group included children who died from accidents. It has been shown that the expression of melatonin receptors as well as serotonin and CD34 angiogenesis markers in tissues of the medulla, heart, and aorta of infants who died from SIDS is statistically lower as compared with their expression in the same tissues in children who died from accidents. The obtained data help to clarify in detail the role of melatonin and such signaling molecules as serotonin and CD34 in SIDS pathogenesis, which can open new prospects for devising novel methods for predictive diagnosis of development and targeted prophylaxis of SIDS.

Persistent Racial/Ethnic Disparities in Supine Sleep Positioning among US Preterm Infants, 2000-2015

OBJECTIVE

To assess trends in racial disparity in supine sleep positioning (SSP) across racial/ethnic groups of infants born early preterm (Early preterm; <34 weeks) and late preterm (Late preterm; 34-36 weeks) from 2000 to 2015.

STUDY DESIGN

We analyzed Pregnancy Risk Assessment Monitoring System data (a population-based perinatal surveillance system) from 16 US states from 2000 to 2015 (Weighted N = 1 020 986). Marginal prevalence of SSP by year was estimated for infants who were early preterm and late preterm, adjusting for maternal and infant characteristics. After stratifying infants who were early preterm and late preterm, we compared the aOR of SSP trends across racial/ethnic groups by testing the time-race interaction.

RESULTS

From 2000 to 2015, Non-Hispanic Black infants had lower odds of SSP compared with Non-Hispanic White infants for early preterm (aOR 0.61; 95% CI 0.47-0.78) and late preterm (aOR 0.44; 95% CI 0.34-0.56) groups. For Hispanic infants, there was no statistically significant difference for either preterm group when compared with Non-Hispanic White infants. aOR of SSP increased (on average) annually by 10.0%, 7.3%, and 7.7%, respectively, in Non-Hispanic White, Non-Hispanic Black, and Hispanic early preterm infants and by 5.8%, 5.9%, and 4.8% among Non-Hispanic White, Non-Hispanic Black, and Hispanic late preterm infants. However, there were no significant between-group differences in annual changes (Early preterm: P = .11; Late preterm: P = .25).

CONCLUSIONS

SSP increased for all racial/ethnic preterm groups from 2000 to 2015. However, the racial/ethnic disparity in SSP among early preterm and late preterm groups persists.

The Mammalian Diving Response: Inroads to Its Neural Control

The mammalian diving response (DR) is a remarkable behavior that was first formally studied by Laurence Irving and Per Scholander in the late 1930s. The DR is called such because it is most prominent in marine mammals such as seals, whales, and dolphins, but nevertheless is found in all mammals studied. It consists generally of breathing cessation (apnea), a dramatic slowing of heart rate (bradycardia), and an increase in peripheral vasoconstriction. The DR is thought to conserve vital oxygen stores and thus maintain life by directing perfusion to the two organs most essential for life-the heart and the brain. The DR is important, not only for its dramatic power over autonomic function, but also because it alters normal homeostatic reflexes such as the baroreceptor reflex and respiratory chemoreceptor reflex. The neurons driving the reflex circuits for the DR are contained within the medulla and spinal cord since the response remains after the brainstem transection at the pontomedullary junction. Neuroanatomical and physiological data suggesting brainstem areas important for the apnea, bradycardia, and peripheral vasoconstriction induced by underwater submersion are reviewed. Defining the brainstem circuit for the DR may open broad avenues for understanding the mechanisms of suprabulbar control of autonomic function in general, as well as implicate its role in some clinical states. Knowledge of the proposed diving circuit should facilitate studies on elite human divers performing breath-holding dives as well as investigations on sudden infant death syndrome (SIDS), stroke, migraine headache, and arrhythmias. We have speculated that the DR is the most powerful autonomic reflex known.

Geographic Variation in Sudden Unexpected Infant Death in the United States

OBJECTIVES

To assess the geographic variation of sudden unexpected infant death (SUID) and test if variation in geographic factors, such as state, latitude, and longitude, play a role in SUID risk across the US.

STUDY DESIGN

We analyzed the Centers for Disease Control and Prevention's Cohort Linked Birth/Infant Death dataset (2005-2010; 22 882 SUID cases, 25 305 837 live births, rate 0.90/1000). SUID was defined as infant deaths (ages 7-364 days) that included sudden infant death syndrome, ill-defined and unknown cause of mortality, and accidental suffocation and strangulation in bed. SUID geographic variation was analyzed using 2 statistical models, logistic regression and generalized additive model (GAM).

RESULTS

Both models produced similar results. Without adjustment, there was marked geographic variation in SUID rates, but the variation decreased after adjusting for covariates including known risk factors for SUID. After adjustment, nine states demonstrated significantly higher or lower SUID mortality than the national average. Geographic contribution to SUID risk in terms of latitude and longitude were also attenuated after adjustment for covariates.

CONCLUSION

Understanding why some states have lower SUID rates may enhance SUID prevention strategies.

Ambient Air Pollution and Sudden Infant Death Syndrome in Korea: A Time-Stratified Case-Crossover Study

Sudden infant death syndrome (SIDS) is an occasional cause of unexpected mortality in infancy. While various etiological factors have been hypothesized, air pollution has been consistently presented as an environmental factor. In this study, we aimed to estimate the risk of SIDS in relation to exposure to air pollution and the effects of its modifying factors. A mortality dataset with supplementary infant mortality survey data from Statistics Korea was used and combined the concentration of ambient air pollution data from AirKorea based on the date of death and residential addresses of the SIDS cases. Odds ratios (ORs) were estimated according to birthweight, gestational age, maternal age, and infant age using a time-stratified case-crossover study design. The risk of exposure to particulate matter of less than 10 μm in diameter (PM₁₀), nitrogen dioxide (NO₂), carbon monoxide (CO), and sulfur dioxide was estimated. The number of deaths due to SIDS was 454 (253 males and 201 females). The OR per 27.8 µg/m³ increment of PM₁₀ was 1.14 (95% confidence interval [CI]: 1.03–1.25) and that per 215.8 ppb of CO was 1.20 (95% CI: 1.03–1.40) in all infants. In females, an increase in NO₂ and CO levels was associated with a higher risk of SIDS in low-birthweight and preterm infants. The OR per 15.7 ppb increment in NO₂ was highest among preterm infants, with a value of 5.12 (95% CI: 1.27–20.63), and low-birthweight individuals, with a value of 4.11 (95% CI: 1.74–9.72), at a moving average of 0 to 3 days. In males, however, no significant association was found. In the present study, exposure to air pollution was associated with an increased risk of SIDS. This association was more evident in susceptible infants with a low-birthweight or in cases of preterm birth.

The Sudden Infant Death Syndrome mechanism of death may be a non-septic hyper-dynamic shock

BACKGROUND

Sudden Infant Death Syndrome (SIDS) mechanisms of death remains obscured. SIDS' Triple Risk Model assumed coexistence of individual subtle vulnerability, critical developmental period and stressors. Prone sleeping is a major risk factor but provide no clues regarding the mechanism of death. The leading assumed mechanisms of death are either an acute respiratory crisis or arrhythmias but neither one is supported with evidence, hence both are eventually speculations. Postmortem findings do exist but are inconclusive to identify the mechanism of death. WHAT DOES THE PROPOSED HYPOTHESIS BASED ON?: 1. The stressors (suggested by the triple risk model) share a unified compensatory physiological response of decrease in systemic vascular resistant (SVR) to facilitate a compensatory increase in cardiac output (CO). 2. The cardiovascular/cardiorespiratory control of the vulnerable infant during a critical developmental period may be impaired. 3. A severe decrease in SVR is associated with hyper-dynamic state, high output failure and distributive shock.

THE HYPOTHESIS

Infant who is exposed to one or more stressors responds normally by decrease in SVR which increases CO. In normal circumstances once the needs are met both SVR and CO are stabilized on a new steady state. The incompetent cardiovascular control of the vulnerable infant fails to stabilize SVR which decreases in an uncontrolled manner. Accordingly CO increases above the needs to hyper-dynamic state, high output heart failure and hyper-dynamic shock.

CONCLUSIONS

The proposed hypothesis provides an appropriate alternative to either respiratory crises or arrhythmia though both speculations cannot be entirely excluded.

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.

Is ambient temperature associated with risk of infant mortality? A multi-city study in Korea

BACKGROUND

Although numerous studies have shown increased risk of mortality from elevated temperatures for adults, limited studies have examined temperature's effect on mortality for infants. Our study investigated the city-specific and overall effects of ambient temperature on infant mortality in seven major cities in Korea, 2004-2007.

METHODS

Birth cohort using a linked birth and death records included 777,570 births with 557 all-cause deaths. We estimated city-specific hazard ratios for each city using an extended Cox proportional hazards model with time-dependent covariates. Then we combined city-specific hazard ratios to generate overall hazard ratio across the seven cities using a Bayesian hierarchical model. Stratified analyses were conducted by cause of death (total and SIDS), exposure period (whole gestation, each trimester, lifetime, 1 month before death, and 2 weeks before death), sex, and maternal characteristics.

RESULTS

Overall across the cities, we found significantly positive associations between ambient temperature during 1 month before death or 2 weeks before death and infant mortality from total or SIDS. The overall hazard ratio of infant mortality from total deaths and SIDS for a 1°C increase during 1 month before death was 1.52 (95% CI, 1.46-1.57) and 1.50 (95% CI, 1.35-1.66), respectively. We also found suggestive evidence that some factors such as mother's age may modify the association.

CONCLUSIONS

Our findings have implications for establishment of policy to reduce the risk of infant mortality from high ambient temperature under climate change.

An Approach to the Classification of Apparent Asphyxial Infant Deaths

Recent evidence indicates that with thorough, high quality death investigations and autopsies, forensic pathologists have recognized that many unexpected infant deaths are, in fact, asphyxial in nature. With this recognition has come a commensurate decrease in, and in some cases, abolition of, the label "sudden infant death syndrome" (SIDS). Current controversies often pertain to how and why some infant deaths are determined to be asphyxial in nature and whether or not apparent asphyxial circumstances are risk factors for SIDS, or rather, harbingers of asphyxial deaths. In an effort to sidestep these controversies, some forensic pathologists elected to instead use the noncommittal label "sudden unexpected infant death" (SUID), leading to the unfortunate consequence of SUID - like SIDS - gaining notoriety as an actual disease that could be diagnosed, studied, and ultimately cured. Although it is not possible to provide death certification guidance for every conceivable type of unexpected infant death, we recognize and propose a simple classification system for overarching themes that cover the vast majority of cases where infants die suddenly and unexpectedly.

Paediatricians' Practice About SUDDEN Infant Death Syndrome in Catalonia, Spain

Background SIDS is the major cause of death among healthy born infants in developed countries. Its causes are still unclear, but its risk can be reduced by implementing some simple active interventions. In Spain, limited attention was given to SIDS by the national healthcare system, and actual data on healthcare professionals' practice on this topic was not available. This study explored for the first time paediatricians' knowledge and practice about SIDS. Methods A cross-sectional survey was carried out between November 2012 and April 2013 in Catalonia, and reached 1202 paediatricians. The response rate was 46%. Results 94% of respondents perceived themselves as qualified for giving advice and recommendations about SIDS to parents, but only 58% recognized the supine position as the safest position and recommended the supine position exclusively to parents. Seniority and 'having received a specific training about SIDS' were detrimental to paediatricians' knowledge. Discussion Efforts should be made in order to improve paediatricians' knowledge and practice about SIDS. Specific refresher trainings are highly recommended, and should especially target paediatricians with higher seniority. These trainings could be provided as optional modules, as we could see that the paediatricians who would most benefit from them are already aware of the need to refresh their knowledge.

Animal models for assessment of infection and inflammation: contributions to elucidating the pathophysiology of sudden infant death syndrome

Sudden infant death syndrome (SIDS) is still not well understood. It is defined as the sudden and unexpected death of an infant without a definitive cause. There are numerous hypotheses about the etiology of SIDS but the exact cause or causes have never been pinpointed. Examination of theoretical pathologies might only be possible in animal models. Development of these models requires consideration of the environmental and/or developmental risk factors often associated with SIDS, as they need to explain how the risk factors could contribute to the cause of death. These models were initially developed in common laboratory animals to test various hypotheses to explain these infant deaths – guinea pig, piglet, mouse, neonatal rabbit, and neonatal rat. Currently, there are growing numbers of researchers using genetically altered animals to examine specific areas of interest. This review describes the different systems and models developed to examine the diverse hypotheses for the cause of SIDS and their potential for defining a causal mechanism or mechanisms.

Sudden unexpected death in infancy: a historical perspective

Epidemiological, developmental and pathological research over the last 40 years has done much to unravel the enigma of sudden unexpected death in infancy (SUDI) and sudden infant death syndrome (SIDS) that has afflicted the human condition for millennia. Modifications in infant care practices based on the avoidance of risk factors identified from a consistent epidemiological profile across time and multiple locations have resulted in dramatic reductions in the incidence of SUDI and SIDS in particular. The definition of SIDS (or unexplained SUDI) has been continually refined allowing enhanced multidisciplinary research, results of which can be more reliably compared between investigators. These latter expanded definitions mandating death scene investigations, evaluation of the circumstances of death and more comprehensive autopsies including additional ancillary testing have illuminated the importance of life-threatening sleep environments. The triple-risk hypothesis for SIDS has been increasingly validated and formulates an inextricable relationship between an infant's state of development, underlying pathological vulnerability and an unsafe sleep environment for sudden infant death to occur. Today, the major risk factors for SUDI are maternal smoking and bed sharing, and the challenge is to implement effective strategies that will reduce the exposure to such risks as was done with prone sleeping position. The challenges ahead include development of clinical methods and/or laboratory testing that will accurately identify which infants are at particularly high risk of SIDS but also means by which their deaths can be prevented.

Speaking discourses and silent lips: women and gender-based portraits in sudden infant death publications

AIMS AND OBJECTIVES

To reveal the prominent discourses and assigned social ordering given to women in paediatric research in Sweden concerning the subject of sudden infant death syndrome.

BACKGROUND

There are no further studies in Sweden and elsewhere, regarding publishing portraits of women's social ordering in nursing research surrounding sudden infant death syndrome.

DESIGN AND METHODS

The material encompassed all 55 articles/comments published by the Swedish Medical Journal 1980-2007 (7 March) as retrieved using selected keywords. The items were accessed in full text, and a discourse analytical approach was used triangulated with feminist theoretical perspectives.

RESULTS

Three main discourses were identified: (1) women as bearers of guilt and accountability, (2) a social ordering where women's biology and lifestyles received great attention together with a tribute to mothers as having the principal responsibility as parent and caregiver and (3) gender-based health policy portrayals showing women/mothers in marginalised social and structural contexts or exposed to one-sided disciplinary penal codes despite the Swedish welfare state having long declared gender equality in its family policies and in paediatric nursing practices.

CONCLUSIONS

Although results from this study primarily relate to the Swedish contexts, they may also reflect the dual role in paediatric nursing practices in other countries, that is, (1) as being medical experts on children's health (paediatrics and nursing) and (2) as change agents with regard to childcare and practical recommendations directed to individuals (mothers, fathers, both or other caregivers of infants).

RELEVANCE TO CLINICAL PRACTICE

The study highlights the needs of not merely seeing the family or the mother as ultimate and individual beneficiaries of medical/practical advice about child-caring duties in infancy. Further studies are encouraged to recognise infant nursing practices, gender equality and safe parenthood in child health research and nursing practices.

Orexin receptors in the developing piglet hypothalamus, and effects of nicotine and intermittent hypercapnic hypoxia exposures

Orexin and its receptors (OxR1 and OxR2) play a significant role in arousal and sleep regulation. Using developing piglets, we aimed to determine the effects of nicotine and Intermittent Hypercapnic Hypoxia (IHH), alone or in combination, on orexin receptor expression in the hypothalamus. Four piglet groups were studied: control (n=14), nicotine (n=14), IHH (n=10) and nic+IHH (n=14). Applying immunohistochemistry for OxR1 and OxR2 expression, eight nuclei/areas of the hypothalamus: dorsal medial nucleus (DMN), arcuate nucleus (ARC), perifornical area (PFA), paraventricular nucleus (PVN), lateral hypothalamic area (LHA), ventral medial nucleus (VMN), supraoptic nucleus, retrochiasmatic part (SONr) and tuberal mammillary nucleus (TMN), were studied. Compared to controls, OxR1 and OxR2 were increased due to exposures, however this was region dependent. Nicotine increased OxR1 in the DMN (P<0.001) and SONr (P=0.036), and OxR2 in the DMN (P<0.001), VMN (P=0.014) and the TMN (P=0.026). IHH increased OxR1 in the DMN, PVN, VMN and SONr (P<0.01 for all), and OxR2 in DMN (P<0.001), PFA (P=0.001), PVN (P=0.004), VMN (P=0.041) and the TMN (P<0.001). The nic+IHH exposure increased OxR1 expression in all nuclei (TMN excluded) however, the changes were not significantly different from IHH alone. For OxR2, the increased expression after nic+IHH was significant compared to IHH in the DMN, ARC and SONr. These results show that nicotine increases orexin receptor expression in a region dependent manner. IHH induced increases were specific to arousal and stress related regions and nic+IHH results suggest that for OxR1, nicotine has no additive effect whereas for OxR2 it does, and is region dependent.

Scientific consensus forum to review the evidence underpinning the recommendations of the Australian SIDS and Kids Safe Sleeping Health Promotion Programme--October 2010

This paper summarises a 1-day scientific consensus forum that reviewed the evidence underpinning the Australian SIDS and Kids Safe Sleeping Health Promotion Programme. The focus was on each of the potentially modifiable risk factors for sudden unexpected deaths in infancy, including sudden infant death syndrome (SIDS) and fatal sleeping accidents. In particular infant sleeping position, covering of the face, exposure to cigarette smoke, room sharing, unsafe sleeping environments, bed sharing, immunisation, breastfeeding, pacifier use and Indigenous issues were discussed in depth. The participants recommended that future 'Reducing the Risk' campaign messages should focus on back to sleep, face uncovered, avoidance of cigarette smoke before and after birth, safe sleeping environment, room sharing and sleeping baby in own cot.

Otolaryngological aspects of sudden infant death syndrome

INTRODUCTION

Sudden infant death syndrome (SIDS) is characterized by the sudden death of an apparently otherwise healthy infant, typically during sleep, and with no obvious case after a thorough post-mortem and scene death examination.

OBJECTIVE

To address the problem from the otolaryngologist's perspective, describe relevant pathologies, discuss controversies and suggest preventive measures in high-risk populations.

METHODOLOGY

A MEDLINE search and hand search were conducted to identify reports published between 1969 and 2011 in the English language on the pathophysiology of SIDS related to the head and neck organs. Search terms included SIDS (MeSH term), SIDS and pathophysiology (text words), and SIDS and autopsy (text words).

DISCUSSION

A growing number of reports suggested head and neck organs involvement in SIDS autopsies. Laryngeal, oropharyngeal, maxillofacial, otologic, cervical vascular abnormalities and infectious etiologies, were recognized and discussed.

CONCLUSIONS

Otolaryngologists should be aware of relevant pathologies, as some are treatable, if identified early enough in infancy. A proactive risk-management approach is warranted in infants presenting with certain abnormalities reviewed here.

Configurative domains in child health research: sudden infant death in the Swedish Medical Journal

The aim of present investigation is to discover publishing portrayals embedded in sudden infant death informatics disseminated by a medical journal at regional level. In particular, gender configurative domains regarding health policy and nursing practices are scrutinized. A qualitative literature review was performed using a critical discourse analytical approach. The full texts of 55 articles/comments published within the field by the Swedish Medical Journal from January 1, 1980 to March 6, 2007 were examined. Four configurative domains were recognized as setting the agenda and as working throughout the reviewed text viz., (a) the clinical-medical episteme, (b) the individualized family domain, (c) gender domains in prevention and nursing practices, and finally (d) the configurative entry into gendered academic writing of the subject in view. The skewed gendered publishing portrayals observed were consistent throughout more than two decades. Gender analysis in child health research is highlighted.

Narratives of deprivation: Women's life stories around Maori sudden infant death syndrome

Maori babies in Aotearoa/New Zealand die of Sudden Infant Death Syndrome (SIDS) at over five times the rate of their non-Maori peers. Research and health promotion around modifiable risk factors has produced only a small improvement in this situation since the mid-1990s. This paper reports on life story interviews, conducted between 2002 and 2004, with nineteen mothers of Maori infants who have died of SIDS. Potential participants were identified and accessed with the support of the national Maori SIDS Prevention Programme care-workers, in both urban and rural locations throughout both main islands of New Zealand. The paper articulates, in a thematic fashion, the bereaved mothers' experiences of alienation, marginalisation and exclusion, as a testimony of lives lived under conditions of serious deprivation in an affluent society. Constructing these experiences as non-modifiable risk factors hinders the development of policy and health promotion interventions that could improve the conditions in which Maori mothers live and raise their babies. It is argued that new approaches that target those whose lives are described here and build on the WHO Social Determinants of Health framework are vital to the efforts of New Zealanders to attain health equity and stem the tide of devastating and preventable loss of Maori babies to SIDS.

Alpha1-syntrophin mutations identified in sudden infant death syndrome cause an increase in late cardiac sodium current

BACKGROUND

Sudden infant death syndrome (SIDS) is a leading cause of death during the first 6 months after birth. About 5% to 10% of SIDS may stem from cardiac channelopathies such as long-QT syndrome. We recently implicated mutations in alpha1-syntrophin (SNTA1) as a novel cause of long-QT syndrome, whereby mutant SNTA1 released inhibition of associated neuronal nitric oxide synthase by the plasma membrane Ca-ATPase PMCA4b, causing increased peak and late sodium current (I(Na)) via S-nitrosylation of the cardiac sodium channel. This study determined the prevalence and functional properties of SIDS-associated SNTA1 mutations.

METHODS AND RESULTS

Using polymerase chain reaction, denaturing high-performance liquid chromatography, and DNA sequencing of SNTA1's open reading frame, 6 rare (absent in 800 reference alleles) missense mutations (G54R, P56S, T262P, S287R, T372M, and G460S) were identified in 8 (approximately 3%) of 292 SIDS cases. These mutations were engineered using polymerase chain reaction-based overlap extension and were coexpressed heterologously with SCN5A, neuronal nitric oxide synthase, and PMCA4b in HEK293 cells. I(Na) was recorded using the whole-cell method. A significant 1.4- to 1.5-fold increase in peak I(Na) and 2.3- to 2.7-fold increase in late I(Na) compared with controls was evident for S287R-, T372M-, and G460S-SNTA1 and was reversed by a neuronal nitric oxide synthase inhibitor. These 3 mutations also caused a significant depolarizing shift in channel inactivation, thereby increasing the overlap of the activation and inactivation curves to increase window current.

CONCLUSIONS

Abnormal biophysical phenotypes implicate mutations in SNTA1 as a novel pathogenic mechanism for the subset of channelopathic SIDS. Functional studies are essential to distinguish pathogenic perturbations in channel interacting proteins such as alpha1-syntrophin from similarly rare but innocuous ones.

SIDS: past, present and future

Despite the large reduction in SIDS mortality, which occurred in the early 1990s following the 'Back to Sleep' campaigns, SIDS remains the leading cause of death in the postneonatal age group. This paper describes the position in the 1980s, the contribution of the New Zealand Cot Death Study, what should be recommended and the current research priorities.

CONCLUSION

SIDS is preventable. Application of what we currently know could eliminate SIDS. The challenge is to find ways of implementing our knowledge.