Choline-acetyltransferase (ChAT) and acetylcholinesterase (AChE) in the human infant dorsal motor nucleus of the Vagus (DMNV), and alterations according to sudden infant death syndrome (SIDS) category.

Amongst other molecules, the cholinergic system consists of choline-acetyltransferase (ChAT, - synthesis enzyme), acetylcholinesterase (AChE - primary hydrolysis enzyme), and butyrylcholinesterase (BuChE - secondary hydrolysis enzyme). In the brainstem, the Dorsal Motor Nucleus of The Vagus (DMNV) has high cholinergic expression and is a region of interest in the neuropathology of sudden infant death syndrome (SIDS). SIDS is the unexpected death of a seemingly healthy infant, but postmortem brainstem abnormalities suggesting altered cholinergic regulation have been found. This study aimed to determine the percentage of positive ChAT and AChE neurons within the infant DMNV through immunohistochemistry at the three levels of the brainstem medulla (caudal, intermediate, and rostral), to investigate whether the proportion of neurons positive for these enzymes differs amongst the diagnostic subgroups of SIDS compared to those with an explained cause of Sudden unexpected death in infancy (eSUDI), and whether there were any associations with SIDS risk factors (male gender, cigarette smoke exposure, co-sleeping/bed sharing, and prone sleeping). Results showed that ChAT-positive neurons were lower in the rostral DMNV in the SIDS II cohort, and within the caudal and intermediate DMNV of infants who were exposed to cigarette smoke. These findings suggest altered cholinergic regulation in the brainstem of SIDS infants, with potential contribution of cigarette smoke exposure, presumably via the nicotinic acetylcholinergic receptor system.

Immunohistochemistry for acetylcholinesterase and butyrylcholinesterase in the dorsal motor nucleus of the vagus (DMNV) of formalin-fixed, paraffin-embedded tissue: comparison with reported literature.

The majority of research regarding the expression of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) in the brain has been conducted using histochemistry to identify enzymatic activity in frozen fixed tissue. However, retrospective human neurochemistry studies are generally restricted to formalin-fixed, paraffin-embedded (FFPE) tissues that are not suitable for histochemical procedures. The availability of commercially available antibody formulations provides the means to study such tissues by immunohistochemistry (IHC). In this study, we optimised IHC conditions for evaluating the expression of AChE and BuChE in the brainstem, focusing on the dorsal motor nucleus of the vagus, in human and piglet FFPE tissues, using commercially available antibodies. Our results were compared to published reports of histochemically determined AChE and BuChE expression. We varied antibody concentrations and antigen retrieval methods, and evaluated different detection systems, with the overall aim to optimise immunohistochemical staining. The primary findings, consistent across both species, are: (1) AChE and BuChE expression dominated in the neuronal somata, specifically in the neuronal cytoplasm; and (2) no change in the protocol resulted in axonal/neuropil expression of AChE. These results indicate that IHC is a suitable tool to detect AChE and BuChE in FFPE tissue using commercial antibodies, albeit the staining patterns obtained differed from those using histochemistry in frozen tissue. The underlying cause(s) for these differences are discussed in detail and may be associated with the principal components of the staining method, the antibody protein target and/or limitations to the detection of epitopes by tissue fixation.

Genes involved in paediatric apnoea and death based on knockout animal models: Implications for sudden infant death syndrome (SIDS).

The mechanism of death in Sudden infant death syndrome (SIDS) remains unknown but it is hypothesised that cardiorespiratory failure of brainstem origin results in early post-natal death. For a subset of SIDS infants, an underlying genetic cause may be present, and genetic abnormalities affecting brainstem respiratory control may result in abnormalities that are detectable before death. Genetic knockout mice models were developed in the 1990s and have since helped to elucidate the physiological roles of a number of genes. This systematic review aimed to identify which genes, when knocked out, result in the phenotypes of abnormal cardiorespiratory control and/or early post-natal death. Three major genes were identified: Pet1- a serotonin transcription factor, the neurotrophin pituitary adenylate cyclase activating polypeptide (PACAP) and its receptor (PAC1). Knockouts targeting these genes had blunted hypercapnic and/or hypoxic responses and early post-natal death. The hypothesis that these genes have a role in SIDS is supported by their being identified as abnormal in SIDS cohorts. Future research in SIDS cohorts will be important to determine whether these genetic abnormalities coexist and their potential applicability as biomarkers.

Expression of reelin with age in the human hippocampal formation.

Reelin plays a key role in neuronal migration and lamination in the cortex and hippocampus. Animal studies have shown that reelin expression decreases with age. The aim of this study was to evaluate the expression of reelin in all layers of the human hippocampal formation across three age groups. We used immunohistochemistry in formalin fixed and paraffin embedded hippocampal tissue from infants (1-10 months; n = 9), children (4-10 years; n = 4), and adults (45-60 years; n = 6) to stain for reelin. Expression was quantified (measured as the number of positive reelin cells/mm2 ) in the granule cell layer of the dentate gyrus (DG), the molecular layer of the dentate gyrus (ML), the hippocampal fissure (HF), stratum lacunosum moleculare (SLM), CA4/Hilus and the stratum pyramidale layer of CA3, CA2, and CA1. Expression of reelin was highest in the HF irrespective of age, followed by the SLM and ML. Minimal to no expression was seen in the stratum pyramidale layer of CA1-3. With age, reelin expression decreased and was statistically significant from infancy to childhood in the HF (p = .02). This study confirms that reelin expression decreases with age in the human hippocampus, and shows for the first time that the major decrease occurs between infancy and early childhood.

Ventilatory support at home for children: A joint position paper from the Thoracic Society of Australia and New Zealand/Australasian Sleep Association.

The goal of this position paper on ventilatory support at home for children is to provide expert consensus from Australia and New Zealand on optimal care for children requiring ventilatory support at home, both non-invasive and invasive. It was compiled by members of the Thoracic Society of Australia and New Zealand (TSANZ) and the Australasian Sleep Association (ASA). This document provides recommendations to support the development of improved services for Australian and New Zealand children who require long-term ventilatory support. Issues relevant to providers of equipment and areas of research need are highlighted.

Cognitive parameters in children with mild obstructive sleep disordered breathing.

PURPOSE: Sleep disordered breathing (SDB) in children is commonly described as a continuum from primary snoring (PS) to obstructive sleep apnea (OSA), based on apnea indices from polysomnography (PSG). This study evaluated the difference in neurocognitive and behavioral parameters, prior to treatment, in symptomatic pre-school children with PSG-diagnosed OSA and PS. METHODS: All children had positive Pediatric Sleep Questionnaire (PSQ) results and were deemed suitable for adenotonsillectomy by an ENT surgeon. Neurocognitive and behavioral data were analyzed in pre-school children at recruitment for the POSTA study (The Pre-School OSA Tonsillectomy Adenoidectomy Study). Data were compared between PS and OSA groups, with Obstructive Apnea-Hypopnea Index, OAHI < 1/h or 1-10/h, respectively. RESULTS: Ninety-one children were enrolled, including 52 with OSA and 39 with PS. Distribution of IQ (using Brief Intellectual Ability, BIA) was slightly skewed towards higher values compared with the reference population. No significant differences were found in neurocognitive or behavioral parameters for children with OSA versus those with PS. DISCUSSION: Neurocognitive and behavioral parameters were similar in pre-school children symptomatic for OSA, regardless of whether or not PSG diagnosed PS or OSA. Despite having identical symptoms, children with PS on PSG are often treated conservatively, whereas those with OSA on PSG are considered for adenotonsillectomy. This study demonstrates that, regardless of whether or not PS or OSA is diagnosed on PSG, symptoms, neurocognition, and behavior are identical in these groups. We conclude that symptoms and behavioral disturbances should be considered in addition to OAHI when determining the need for treatment. TRIAL REGISTRATION: Australian and New Zealand Clinical Trials registration number ACTRN12611000021976.

Relationship between sleep respiration, architecture and childhood enuresis: Correlates between polysomnography and questionnaire.

AIM: Nocturnal enuresis (NE) and sleep-disordered breathing (SDB) are common in childhood. While the two disorders are linked, those links are still being clarified. METHODS: This study compared sleep profiles and enuresis-related behaviours between children with NE and those without, who were referred to a tertiary sleep unit with suspected SDB, using the combination of polysomnography (PSG) and questionnaire. Continuous numerical data were analysed after adjusting for body mass index z-score. RESULTS: The study included 52 Children (39 boys, 13 girls) aged 5-14 years. Twenty-one had enuresis (10 monosymptomatic enuresis (MNE) and 11 non-monosymptomatic enuresis (NMNE)) and 31 did not have enuresis. The majority had comorbidities. On PSG, all children with NE had moderate obstructive sleep apnoea (OSA) compared to the control group which were of mild OSA. Children with NMNE had a higher percentage time in stage-3 non-REM sleep when compared to the non-enuretic and MNE groups (P < 0.05). On the questionnaire, more parents of the NE groups reported that their child was 'difficult to wake in the morning' (P < 0.05). CONCLUSION: In this heterogeneous population referred for suspected SDB, children with NE had moderate OSA, yet those with MNE had increased arousals and more often report difficulty waking than children with suspected SDB who do not wet, while children with NMNE exhibit changes in sleep architecture suggesting deeper sleep. These differences may impact treatment choices for children with enuresis.

The α3 and α4 nicotinic acetylcholine receptor (nAChR) subunits in the brainstem medulla of sudden infant death syndrome (SIDS).

SIDS occurs in early infancy and predominantly during a sleep period. Abnormalities in nicotine receptor binding and in the expression of the nicotinic acetylcholine receptor (nAChR) subunits α7 and ß2 have been reported in the brainstem of SIDS infants. This study focuses on the α3 and α4 nAChR subunits as α3 is important for early postnatal survival while α4 is crucial for nicotine-elicited antinociception and sleep-wake cycle regulation. Tissue from the rostral medulla of infants who died with a known cause of death (eSUDI, n = 7), and from SIDS classified as SIDS I (n = 8) and SIDS II (n = 27), was immunohistochemically stained for the α3 and α4 nAChR subunits and quantified in 9 nuclei comparing amongst these groups. The association with risk factors of sex, cigarette smoke exposure, upper respiratory tract infection (URTI), prone sleeping and bedsharing was also evaluated. Results showed that only α4 changes (increase) were evident in SIDS, occurring in the hypoglossal and cuneate nuclei of SIDS II infants and the nucleus of the spinal trigeminal tract of SIDS I infants. Amongst the SIDS infants, cigarette smoke exposure was only associated with decreased α4 in cribriform fibre tracts, while sex and bedsharing were associated with increases in α3 in the dorsal motor nucleus of the vagus and solitary nucleus, respectively. Combined, these findings suggest that abnormalities in endogenous acetylcholine synthesis and regulation may underlie the altered α3 and α4 nAChR subunit expressions in the SIDS brainstem medulla since the changes were not related to cigarette smoke exposure.

Cell death in the human infant central nervous system and in sudden infant death syndrome (SIDS).

The brainstem has been a focus of sudden infant death syndrome (SIDS) research with amassing evidence of increased neuronal apoptosis. The present study extends the scope of brain regions examined and determines associations with known SIDS risk factors. Immunohistochemical expression of cell death markers, active caspase-3 and TUNEL, was studied in 37 defined brain regions in infants (aged 1-12 months) who died suddenly and unexpectedly (SUDI). A semi-quantitative mean score of marker expression was derived for each region and scores compared between three SUDI subgroups: explained SUDI (eSUDI; n = 7), SIDS I (n = 8) and SIDS II (n = 13). In eSUDI, active caspase-3 scores were highest in several nuclei of the rostral medulla, and lowest in the hypothalamus and cerebellar grey matter (GM). TUNEL was highest in regions of the hippocampus and basal ganglia, and lowest in the thalamus and cerebellar GM. TUNEL scores were higher in SIDS II compared to eSUDI in the amygdala (p = 0.03) and 5/9 nuclei in the rostral medulla (p = 0.04 - 0.01), and higher in SIDS II compared to SIDS I in the amygdala (p < 0.01), putamen (p = 0.01), lentiform nucleus (p = 0.03) and parietal (p = 0.03) and posterior frontal (p = 0.02) cortex. Active caspase-3 was greater in the hypoglossal nucleus (p = 0.03) of SIDS I compared to eSUDI infants. Co-sleeping, cigarette smoke exposure and the presence of an upper respiratory tract infection in SIDS infants was associated with differences in marker expression. This study affirms the sensitivity of the brainstem medulla to cell death in SIDS, and highlights the amygdala as a new region of interest.

Snoring and stertor are associated with more sleep disturbance than apneas and hypopneas in pediatric SDB.

PURPOSE: Polysomnography is not recommended for children at home and does not adequately capture partial upper airway obstruction (snoring and stertor), the dominant pathology in pediatric sleep-disordered breathing. New methods are required for assessment. Aims were to assess sleep disruption linked to partial upper airway obstruction and to evaluate unattended Sonomat use in a large group of children at home. METHODS: Children with suspected obstructive sleep apnea (OSA) had a single home-based Sonomat recording (n = 231). Quantification of breath sound recordings allowed identification of snoring, stertor, and apneas/hypopneas. Movement signals were used to measure quiescent (sleep) time and sleep disruption. RESULTS: Successful recordings occurred in 213 (92%) and 113 (53%) had no OSA whereas only 11 (5%) had no partial obstruction. Snore/stertor occurred more frequently (15.3 [5.4, 30.1] events/h) and for a longer total duration (69.9 min [15.7, 140.9]) than obstructive/mixed apneas and hypopneas (0.8 [0.0, 4.7] events/h, 1.2 min [0.0, 8.5]); both p < 0.0001. Many non-OSA children had more partial obstruction than those with OSA. Most intervals between snore and stertor runs were < 60 s (79% and 61% respectively), indicating that they occur in clusters. Of 14,145 respiratory-induced movement arousals, 70% were preceded by runs of snore/stertor with the remainder associated with apneas/hypopneas. CONCLUSIONS: Runs of snoring and stertor occur much more frequently than obstructive apneas/hypopneas and are associated with a greater degree of sleep disruption. Children with and without OSA are frequently indistinguishable regarding the amount, frequency, and the degree of sleep disturbance caused by snoring and stertor.

Biochemical markers of cardiac dysfunction in children with obstructive sleep apnoea (OSA).

OBJECTIVES: We explored relationships between biochemical markers and cardiac responses of children with and without obstructive sleep apnoea (OSA) during exercise. We hypothesised that serum markers of sympathetic nervous system activity and low-grade inflammation would correlate with cardiac responses to exercise in children with or without OSA. METHODOLOGY: The study included 40 of 71 children with previously characterised responses to cardiopulmonary exercise testing. Measures included serum cytokine levels using a multiplex bead-based assay (interleukins IL-1ß, IL-2, IL-4, IL-6, IL-8, IL-10, TNF-α and IFN-γ). Serum amyloid A (SAA) was quantified by nephelometry, and metanephrine/normetanephrine levels were measured by liquid chromatography, mass-spectroscopy. Comparisons were made between children with and without OSA, and with and without obesity. Relationships between biomarkers and various cardiac parameters were explored by linear regression. RESULTS: Amongst the 40 children in this study, OSA was present in 23. Compared to the 17 children without OSA, those with OSA had higher resting serum IL-6 levels compared to those without (median 3.22 pg/ml vs. 2.31, p < 0.05). Regarding correlations with cardiac function after adjusting for OSA, IL-8 negatively correlated to heart rate (HR) response following exercise (p = 0.03) and IFN-γ negatively correlated with Stroke Volume Index (SVI) (p = 0.03). Both metanephrine and normetanephrine levels positively correlated with SVI (p = 0.04, p = 0.047; respectively) and QI (p = 0.04, p = 0.04; respectively) during exercise when adjusting for OSA. CONCLUSIONS: Children with OSA have raised morning levels of serum IL-6. Separately, higher levels of IFN-γ and IL-8 and lower levels of metanephrine and normetanephrine related to poorer cardiac function during exercise.

Neuronal apoptosis in the brainstem medulla of sudden unexpected death in infancy (SUDI), and the importance of standardized SUDI classification.

The purpose of this study was to examine the neuronal expression of apoptotic markers in the rostral medulla of a newly characterized dataset of sudden unexpected death in infancy (SUDI), and to determine the impact of diagnostic groupings on these findings and whether they pertain to the intrinsic apoptotic pathway. Immunohistochemical staining was quantified to determine the percentage of neurons positive for active caspase-9 (specific to the intrinsic apoptotic pathway), active caspase-3 (common to the intrinsic and extrinsic apoptotic pathways) and Terminal deoxynucleotidyl transferase mediated dUTP nick-end labelling (TUNEL) (labels DNA fragmentation) in nine nuclei of the rostral medulla. Expression was compared between groups of SUDI infants where the cause of death was initially classified by a forensic pathologist or subsequently after reclassification by an expert panel using the San Diego Criteria. 68 SUDI infants were studied and originally classified as explained SUDI (n = 12), Sudden Infant Death Syndrome (SIDS) (n = 27) and undetermined (n = 29). Reclassification resulted in a decrease in the number of explained SUDI cases to 7 and a decrease in the number of undetermined cases to 4, with a corresponding increase in the number of SIDS cases to 57 (8 SIDS I; 49 SIDS II). The expression of apoptotic markers was similar in explained SUDI and SIDS I infants. However, TUNEL expression was greater in the cuneate (p < 0.001), vestibular (p = 0.01) and hypoglossal (p < 0.001) nuclei and active caspase-3 expression was lower in the arcuate nucleus (p = 0.037) in SIDS II compared to explained Sudden Unexpected Death in Infancy (eSUDI) infants. Compared to SIDS I infants, SIDS II infants had greater TUNEL expression in the dorsal motor nucleus of the vagus (p < 0.01) and greater active caspase-9 expression in the medial and spinal vestibular nuclei (p = <0.01). Changes in apoptotic expression predominated in SIDS II infants. We postulate that these are due to a combination of contributing risk factors including the presence of an upper respiratory tract infection and bed-sharing/co-sleeping. The absence of changes in active caspase-9 expression compared to eSUDI indicates that the intrinsic apoptotic pathway is not upregulated in SIDS.

Rationale for and design of the "POSTA" study: Evaluation of neurocognitive outcomes after immediate adenotonsillectomy compared to watchful waiting in preschool children.

BACKGROUND: IQ deficits are linked to even mild obstructive sleep apnoea (OSA) in children. Although OSA is commonly first diagnosed in the pre-school age group, a randomised trial is still needed to assess IQ outcomes after adenotonsillectomy in the pre-school age-group. This randomised control trial (RCT) will primarily determine whether adenotonsillectomy improves IQ compared to no adenotonsillectomy after 12 months, in preschool (3-5 year-old) children with mild to moderate OSA. METHODS: This protocol is for an ongoing multi-centred RCT with a recruitment target of 210 subjects (105 in each arm). Children age 3-5 years with symptoms of OSA, are recruited through doctor referral, at the point of referral to the Ear Nose and Throat (ENT) services. Screening is initially with a questionnaire (Paediatric Sleep Questionnaire, PSQ) for symptoms of obstructive sleep apnoea (OSA). Where questionnaires are positive (suggestive of OSA) and ENT surgeons recommend them for adenotonsillectomy, they are invited to participate in POSTA. Baseline testing includes neurocognitive testing (IQ and psychometric evaluation with the neuropsychologist blinded to randomisation) and overnight polysomnography (PSG). Where the Obstructive Apnoea-Hypopnea Index (OAHI) from the PSG is <10/h per hour, consent for randomisation is sought; children with severe OSA (OAHI ≥ 10/h) are sent for immediate treatment and excluded from the study. After consent is obtained, participants are randomised to early surgery (within 2 months) or to surgery after a usual wait time of 12 months. Follow-up studies include repeat neurocognitive testing and PSG at 12 (with the waiting list group studied before their surgery) and 24 months after randomisation. Analysis will be by intention to treat. The primary outcome is IQ at 12 months' follow-up. DISCUSSION: If IQ deficits associated with OSA are reversible 12 months after adenotonsillectomy compared to controls, future clinical practice advise would be to undertake early surgery in young children with OSA. The study could provide data on whether a window of opportunity exists for reversing IQ deficits linked to OSA in the pre-school age-group. TRIAL REGISTRATION: Australian and New Zealand Clinical Trials Registration Number ACTRN12611000021976 .

Changes in orexinergic immunoreactivity of the piglet hypothalamus and pons after exposure to chronic postnatal nicotine and intermittent hypercapnic hypoxia.

We recently showed that orexin expression in sudden infant death syndrome (SIDS) infants was reduced by 21% in the hypothalamus and by 40-50% in the pons as compared with controls. Orexin maintains wakefulness/sleeping states, arousal, and rapid eye movement sleep, abnormalities of which have been reported in SIDS. This study examined the effects of two prominent risk factors for SIDS, intermittent hypercapnic hypoxia (IHH) (prone-sleeping) and chronic nicotine exposure (cigarette-smoking), on orexin A (OxA) and orexin B (OxB) expression in piglets. Piglets were randomly assigned to five groups: saline control (n = 7), air control (n = 7), nicotine [2 mg/kg per day (14 days)] (n = 7), IHH (6 min of 7% O2 /8% CO2 alternating with 6-min periods of breathing air, for four cycles) (n = 7), and the combination of nicotine and IHH (N + IHH) (n = 7). OxA/OxB expression was quantified in the central tuberal hypothalamus [dorsal medial hypothalamus (DMH), perifornical area (PeF), and lateral hypothalamus], and the dorsal raphe, locus coeruleus of the pons. Nicotine and N + IHH exposures significantly increased: (i) orexin expression in the hypothalamus and pons; and (ii) the total number of neurons in the DMH and PeF. IHH decreased orexin expression in the hypothalamus and pons without changing neuronal numbers. Linear relationships existed between the percentage of orexin-positive neurons and the area of pontine orexin immunoreactivity of control and exposure piglets. These results demonstrate that postnatal nicotine exposure increases the proportion of orexin-positive neurons in the hypothalamus and fibre expression in the pons, and that IHH exposure does not prevent the nicotine-induced increase. Thus, although both nicotine and IHH are risk factors for SIDS, it appears they have opposing effects on OxA and OxB expression, with the IHH exposure closely mimicking what we recently found in SIDS.

Objective adherence to positive airway pressure therapy in an Australian paediatric cohort.

PURPOSE: This study aimed to objectively measure adherence (compliance) and effectiveness of CPAP and BiLevel pressure support in an Australian paediatric population and determine factors associated with adherence outcomes. METHODS: Data was collected as part of routine clinical care from 2011 to 2013. Adherence was recorded by downloads from the PAP device. "Adequate" adherence was defined as ≥4 h/night for 70 % of days used. Effectiveness of therapy was measured by polysomnography (PSG) pre- and post-PAP initiation. One year follow-up was undertaken to determine the long-term utilisation of PAP therapy. RESULTS: Ninety-nine children were included (55 CPAP, 44 BiLevel). Mean age and BMI z-score were 6.9 ± 5.5 years and 0.1 ± 2.0 for CPAP and 9.8 ± 5.9 years and -0.5 ± 2.6 for BiLevel, respectively. At initial download, adequate adherence was observed in 75 % of CPAP and 91 % of BiLevel users. Mean hours of use (per night) for all nights used was 6.8 ± 2.8 and 9.3 ± 3.6 h, respectively. PSG demonstrated that CPAP use was associated with >60 % decrease in the obstructive apnoea hypopnoea index (OAHI, 19.0 ± 18.4 to 2.4 ± 3.1; p < 0.001). BiLevel use was associated with improved baseline SaO2 and TcCO2 (SaO2, 92.5 ± 5.4 % to 95.5 ± 2.9 %; p = 0.001 and reduction in TcCO2, 50.0 ± 10.9 mmHg to 44.8 ± 7.6 mmHg; p = 0.01). At follow-up, 22 (40 %) patients on CPAP and 26 (59 %) on BiLevel continued with therapy, and amongst these, adequate adherence was maintained in 76 % of CPAP and 80 % of Bilevel users. CONCLUSIONS: In this Australian paediatric cohort (predominantly non-obese), adherence with BiLevel was greater than for CPAP. Over half of our population continue to utilise PAP therapy 1 year later, and amongst these cases, adequate adherence was maintained.

Decreased orexin (hypocretin) immunoreactivity in the hypothalamus and pontine nuclei in sudden infant death syndrome.

Infants at risk of sudden infant death syndrome (SIDS) have been shown to have dysfunctional sleep and poor arousal thresholds. In animal studies, both these attributes have been linked to impaired signalling of the neuropeptide orexin. This study examined the immunoreactivity of orexin (OxA and OxB) in the tuberal hypothalamus (n = 27) and the pons (n = 15) of infants (1-10 months) who died from SIDS compared to age-matched non-SIDS infants. The percentage of orexin immunoreactive neurons and the total number of neurons were quantified in the dorsomedial, perifornical and lateral hypothalamus at three levels of the tuberal hypothalamus. In the pons, the area of orexin immunoreactive fibres were quantified in the locus coeruleus (LC), dorsal raphe (DR), laterodorsal tegmental (LDT), medial parabrachial, dorsal tegmental (DTg) and pontine nuclei (Pn) using automated methods. OxA and OxB were co-expressed in all hypothalamic and pontine nuclei examined. In SIDS infants, orexin immunoreactivity was decreased by up to 21 % within each of the three levels of the hypothalamus compared to non-SIDS (p ≤ 0.050). In the pons, a 40-50 % decrease in OxA occurred in the all pontine nuclei, while a similar decrease in OxB immunoreactivity was observed in the LC, LDT, DTg and Pn (p ≤ 0.025). No correlations were found between the decreased orexin immunoreactivity and previously identified risk factors for SIDS, including prone sleeping position and cigarette smoke exposure. This finding of reduced orexin immunoreactivity in SIDS infants may be associated with sleep dysfunction and impaired arousal.

Developmental changes in sleep and breathing across infancy and childhood.

Sleep and breathing are physiological processes that begin in utero and undergo progressive change. While the major period of change for both sleep and breathing occurs during the months after birth, considered a period of vulnerability, more subtle changes continue to occur throughout childhood. The systems that control sleep and breathing develop separately, but sleep represents an activity state during which breathing and breathing control is significantly altered. Infants and young children may spend up to 12 hours a day sleeping; therefore, the effects of sleep on breathing are fundamental to understanding both processes in childhood. This review summarizes the current literature relevant to understanding the normal development of sleep and breathing across infancy and childhood.

Neurochemical abnormalities in the brainstem of the Sudden Infant Death Syndrome (SIDS).

The brainstem has been a focus in Sudden Infant Death Syndrome (SIDS) research for 30 years. Physiological and animal model data show that cardiorespiratory, sleep, and arousal mechanisms are abnormal after exposure to SIDS risk factors or in infants who subsequently die from SIDS. As the brainstem houses the regulatory centres for these functions, it is the most likely site to find abnormalities. True to this hypothesis, data derived over the last 30 years shows that the brainstem of infants who died from SIDS exhibits abnormalities in a number of major neurotransmitter and receptor systems including: catecholamines, neuropeptides, acetylcholinergic, indole amines (predominantly serotonin and its receptors), amino acids (predominantly glutamate), brain derived neurotrophic growth factor (BDNF), and some cytokines. A pattern is emerging of particular brainstem nuclei being consistently affected including the dorsal motor nucleus of the vagus (DMNV), nucleus of the solitary tract (NTS), arcuate nucleus (AN) and raphe. We discuss the implications of these findings and directions that this may lead in future research.

Exploratory study of sleeping patterns in children admitted to hospital.

AIMS: Sleep is considered an important time of healing and restoration during illness. The primary aim of this study was to determine the prevalence of self-reported sleep disturbance in children admitted to a tertiary children's hospital with a variety of medical diagnoses. METHODS: Parents of children admitted to the hospital, aged between 1 and 18 years, were asked to complete a sleep diary during one night of their child's hospital stay. Children older than 12 years were asked to complete a diary independently. Descriptive statistics were used to summarise the data. RESULTS: Overall, 107 children were surveyed for one hospital inpatient night. The overall prevalence of poor sleep was 52.3%. The wide age range and variety of diagnosis limited further detailed analysis of specific causes of this problem. Poor sleep prior to admission was the strongest predictor of poor sleep in hospital suggesting that these children already had an underlying sleep problem. Unprompted awakenings were predominantly due to toileting (17.8%) or were spontaneous (17.8%). Factors specific to the hospital environment that woke children were nursing cares (25.2%), alarms (12.1%) and pain (12.1%). CONCLUSIONS: Children admitted to hospital have a higher prevalence of poor sleep compared with healthy children in the community. Children were woken frequently by both external noise and attention provided by hospital staff. Education of hospital staff about the importance of sleep for children and factors that affect children's sleep may reduce the negative impact of hospitalisation on children's sleep.