Fewer spontaneous arousals in infants with apparent life-threatening event

STUDY OBJECTIVES

A deficit in arousal process has been implicated as a mechanism of sudden infant death syndrome (SIDS). Compared with control infants, SIDS victims showed significantly more subcortical activations and fewer cortical arousals than matched control infants. Apparent life-threatening event (ALTE) is often considered as an aborted SIDS event. The aim of this study was to study the arousal characteristics of ALTE infants during the first months of life.

DESIGN

35 ALTE infants were studied with nighttime polysomnography at 2-3, 5-6, and 8-9 months of age. Eighteen of the infants had mothers who smoked. The infants were born full term and were usually supine sleepers. Sleep state and cardiorespiratory parameters were scored according to recommended criteria. Arousals were differentiated into subcortical activations or cortical arousals, according to the presence of autonomic and/or electroencephalographic changes. The results were compared with those of 19 healthy infants with nonsmoking mothers.

RESULTS

During NREM sleep, the ALTE infants had fewer total arousals, cortical arousals, and subcortical activations at 2-3 and 5-6 months (P < 0.001) than control infants. ALTE infants with smoking mothers had more obstructive apnea (P = 0.009) and more subcortical activations during REM sleep at 2-3 months of age (P < 0.001) than ALTE infants with nonsmoking mothers.

CONCLUSIONS

Spontaneous arousals were differently altered in ALTE infants than in SIDS infants, suggesting an entity different from SIDS. ALTE infants with smoking mothers had arousal and respiratory characteristics that were similar to future SIDS victims, suggesting some common abnormalities in brainstem dysfunction.

Maturation of spontaneous arousals in healthy infants

OBJECTIVE

The propensity to arouse from sleep is an integrative part of the sleep structure and can have direct implications in various clinical conditions. This study was conducted to evaluate the maturation of spontaneous arousals during the first year of life in healthy infants.

DESIGN

Nineteen infants were studied with nighttime polysomnography on 3 occasions: aged 2 to 3 months, 5 to 6 months, and 8 to 9 months. Ten infants with a median age of 3 weeks were added to the main study to assess the maturation of arousals from birth. The infants were born full-term, were healthy at the time of study, and had no history of apnea. Sleep-state and cardiorespiratory parameters were scored according to recommended criteria. Arousals were differentiated into subcortical activations or cortical arousals, according to the presence of autonomic and/or electroencephalographic changes. Frequencies of subcortical activations and cortical arousals were studied at different ages in both rapid eye movement (REM) and non-rapid eye movement (NREM) sleep.

RESULTS

During sleep time, the frequency of total arousals, cortical arousals, and subcortical activations decreased with age. The maturation of the arousal events differed according to sleep states and types of arousals. With age, cortical arousals increased in REM sleep (P = 0.006) and decreased in NREM sleep (P = 0.01). Subcortical activations decreased with age in REM (P < 0.001) and NREM sleep (P < 0.001).

CONCLUSIONS

During total sleep time, the frequency of cortical arousals and subcortical activations decreased with maturation. However, the maturation process was different between cortical arousals and subcortical activations. This finding suggests a difference in the maturational sequence of the different brain centers regulating arousals.

Spontaneous Arousability in Prone and Supine Position in Healthy Infants

STUDY OBJECTIVE

Compared with control infants, those who will be future victims of sudden infant death syndrome (SIDS) show a decreased arousability during sleep, with fewer cortical arousals and more-frequent subcortical activations. These findings suggest an incomplete arousal process in victims of SIDS. Prone sleep position, a major risk factor for SIDS, has been reported to reduce arousal responses during sleep. The present study was undertaken to evaluate whether the prone sleep position impairs the arousal process in healthy infants.

METHODS

Twenty-four healthy infants were studied polygraphically during 1 night; 12 infants regularly slept supine and 12 infants regularly slept prone. Infants were matched for sex, gestational age, and age at recording. Arousals were differentiated into subcortical activations or cortical arousals, according to the presence of autonomic and/or electroencephalographic changes. Frequencies of subcortical activations and cortical arousals were compared in the prone- and the supine-sleeping infants.

RESULTS

Compared with supine sleepers, prone sleepers had significantly fewer cortical arousals during rapid eye movement (REM) sleep (p = .043). There were no significant differences in cortical arousals between the 2 groups during non-REM sleep. No significant differences were seen in the frequencies of subcortical activations during both REM and non-REM sleep between supine and prone sleepers. The ratio of cortical arousal to subcortical activation showed no significant differences between the prone and the supine sleepers.

CONCLUSIONS

Prone sleep position decreased the frequency of cortical arousals but did not change the frequency of subcortical activations, as has been previously found in SIDS victims. These results suggest specific pathways for impairment of the arousal process in SIDS victims.

Apnea, glial apoptosis and neuronal plasticity in the arousal pathway of victims of SIDS

Of 27,000 infants whose sleep-wake characteristics were studied under the age of 6 months, 38 died unexpectedly 2-12 weeks after the sleep recording in a pediatric sleep laboratory. Of these infants, 26 died of sudden infant death syndrome (SIDS), and 12 of definitely identified causes. The frequency and duration of sleep apneas were analysed. Sleep recordings and brainstem histopathology were studied to elucidate the possible relationship between sleep apnea and neuropathological changes within the arousal system. Immunohistochemical analyses were conducted using tryptophan hydroxylase (TrypH), a serotonin synthesizing enzyme, and growth-associated phosphoprotein 43 (GAP43), a marker of synaptic plasticity. The terminal-deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method was used for apoptosis. The pathological and physiological data were correlated for each infant. In the SIDS victims, statistically significant positive correlations were seen between the number of TrypH-positive neurons in the dorsal raphe nucleus of the midbrain and the duration of central apneas (p = 0.03), between the number of TUNEL-positive glial cells in the pedunculopontine tegmental nucleus (PPTN) and the average number of spines in GAP43-positive neurons in the PPTN (p = 0.04). These findings in the dorsal raphe nucleus of the midbrain and PPTN, that play important roles in the arousal pathway suggest a possible link between changes in arousal and SIDS.

Serotonergic receptors in the midbrain correlated with physiological data on sleep apnea in SIDS victims

BACKGROUND

Recently it has been reported that serotonin and related matters are associated with the sudden infant death syndrome (SIDS), which is still the main cause of postneonatal infant death. To further explore this claim, the correlation between serotonin receptors in the brainstem and sleep apnea in SIDS victims was investigated.

MATERIALS AND METHODS

Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age including 26 cases of SIDS. All the infants had been recorded during one night in a pediatric sleep laboratory some 3-12 weeks before death. The frequency and duration of sleep apnea were analyzed. Brainstem material was collected and immunohistochemistry on 5-hydroxy tryptamine 1A (5HT1A) receptor was carried out. The density of 5HT1A receptor-positive neurons was measured quantitatively. Nonparametric analysis of the density of 5HT1A receptor-positive neurons was carried out between SIDS and non-SIDS cases. Correlation analyses were performed between the density of 5HT1A receptor-positive neurons and the data on sleep apnea.

RESULTS

There was no correlation between the pathological data on 5HT1A receptors and the physiological data on sleep apnea in SIDS victims.

CONCLUSIONS

No correlation between pathological findings of serotonin and physiological findings of sleep apnea were not in agreement with the association of sleep apnea in pathophysiology of SIDS.

The correlation between ubiquitin in the brainstem and sleep apnea in SIDS victims

BACKGROUND

The sudden infant death syndrome (SIDS) is still the main cause of postneonatal infant death and its etiology has stimulated many competing theories, among which is the role of hypoxia and brainstem abnormalities. One report claims an increased in ubiquitin in the liver of SIDS victims, ubiquitin being one of the heat-shock proteins. The correlation between ubiquitin in the brainstem and sleep apnea in SIDS was investigated here.

MATERIALS AND METHODS

Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age, including 26 cases of SIDS. All the infants had been recorded during one night in a pediatric sleep laboratory some 3-12 weeks before death. The frequency and duration of sleep apnea were analyzed. Brainstem material was collected at autopsy and examined immunohistochemically for ubiquitin. The density of ubiquitin-positive elements was measured semiquantitatively. Correlation analyses were carried out between the density of ubiquitin-positive elements and the data on sleep apnea.

RESULTS

In the victims of SIDS, a statistically significant positive correlation was found between the density of ubiquitin-positive neuronal factors in the pons and the frequency of obstructive apnea (p=0.001) and statistically significant negative correlations were seen between the density of ubiquitin-positive cells in the ependyma in the pons and the duration of obstructive apnea (p=0.044) and between the density of ubiquitin-positive cells in the subependyma in the medulla and the frequency of central apnea (p=0.024).

CONCLUSIONS

It was found that three significant associations existed between the pathological data referring to ubiquitin and physiological data in SIDS victims. These facts are in agreements with the association of sleep apnea in SIDS.

The relationship between neuronal plasticity and serotonergic neurons in the brainstem of SIDS victims

BACKGROUND

The sudden infant death syndrome (SIDS) is still the main cause of postneonatal infant death and its cause is still unknown. Recently, the medullary serotonergic network deficiency theory has been proposed and an association between SIDS and neuronal plasticity has also been suggested. The growth-associated phosphoprotein 43 (GAP43) is a marker of synaptic plasticity and is critical for normal development of the serotonergic innervation. Therefore, the characteristics of GAP43-positive elements and their association with serotonergic neurons were here investigated in the brainstem of SIDS victims.

MATERIALS AND METHODS

The materials of this study included 26 cases of SIDS and 12 control cases. The brainstem material was collected and the immunohistochemistry of GAP43 and tryptophan hydroxylase (TrypH) carried out. The density of GAP43-positive neurons and dendrites and of TrypH-positive neurons were measured quantitatively. Nonparametric analyses of GAP43 between SIDS and non-SIDS and correlation analyses between GAP43 and TrypH were performed.

RESULTS

No significant difference in GAP43-associated findings was found between SIDS and non-SIDS nor any significant correlation between GAP43-associated findings and TrypH-positive neurons.

CONCLUSIONS

The results of this study were not in agreement with the association of GAP43 with SIDS and with serotonergic innervation in SIDS.

Clinicopathological correlation between brainstem gliosis using GFAP as a marker and sleep apnea in the sudden infant death syndrome

BACKGROUND

Chronic hypoxia, leading to brainstem gliosis, has been postulated as a factor in the sudden infant death syndrome (SIDS), which is still the main cause of postneonatal infant death. Gliosis detected by immunohistochemistry of glial fibrillary acidic protein (GFAP) is a marker of apoptosis. The correlation between GFAP-positive reactive astrocytes in the brainstem and sleep apnea in SIDS was investigated.

MATERIALS AND METHODS

Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age, including 26 cases of SIDS. The frequency and duration of sleep apnea were analyzed. Brainstem material was collected and immunohistochemistry of GFAP carried out. The density of GFAP-positive reactive astrocytes was measured quantitatively. Correlation analyses were carried out between the data on gliosis and the physiological data of sleep apnea.

RESULTS

A SIDS-specific negative correlation between the density of gliosis in the dorsal vagus nucleus in the medulla oblongata and the frequency of obstructive apnea (p=0.022) was found.

CONCLUSIONS

A significant SIDS-specific correlation with gliosis in the dorsal vagus nucleus and the characteristics of sleep apnea might invite the cardiorespiratory changes in SIDS.

Pathological data on apoptosis in the brainstem and physiological data on sleep apnea in SIDS victims

The sudden infant death syndrome (SIDS) is still the main cause of postneonatal infant death and its cause is still unknown. A chronic hypoxic situation has been shown to exist in the brains of SIDS victims and apoptosis has been demonstrated in hypoxic situations. In this study, the correlation between apoptotic neurons or glias and sleep apnea in SIDS was investigated in the brainstem of SIDS victims.

MATERIALS AND METHODS

In a cohort of 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age. They included 26 cases of SIDS. The frequency and duration of sleep apnea were analyzed. The brainstem material was collected and terminal-deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) method was carried out. The density of TUNEL-positive neurons or glias was measured quantitatively. Correlation analyses were carried out between the apoptosis-associated pathological data and the physiological data of sleep apnea.

RESULTS

No significant negative or positive correlation between the density of TUNEL-positive neurons or glias and the characteristics of sleep apnea was observed in SIDS victims. No statistically significant differences associated with apoptotic neurons and glias were observed between SIDS and non-SIDS.

CONCLUSIONS

The pathological findings of apoptosis were not in agreement with the hypothesis refer to apnea and arousal phenomenon in pathophysiology of SIDS.

Substance P in the midbrains of SIDS victims and its correlation with sleep apnea

BACKGROUND

Substance P (SP) is a neuropeptide transmitter found in sensory neurons of the central nervous system and related to pain sensation and respiratory regulation. Some reports claim an increase in SP in the brains of SIDS victims, so the correlation between SP and sleep apnea was investigated here.

MATERIALS AND METHODS

Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age, which included 26 cases of Sudden Infant Death Syndrome (SIDS). All the infants had been recorded during one night in a pediatric sleep laboratory some 3 to 12 weeks before death. The frequency and duration of sleep apnea were analyzed. Brainstem material was collected and immunohistochemistry for SP was carried out. The density of SP positive fibers was measured in the nucleus spinal and mesencephalic nervi trigemini and nucleus parabranchialis in the brainstem of abovementioned cases. Correlation analyses were carried out between the density of SP and the data of sleep apnea.

RESULTS

There was no SIDS specific correlation of SP through the above-listed parts of the midbrain with frequency and duration of sleep apnea.

CONCLUSIONS

There was no significant association between the SP findings and apnea data in SIDS; this is not in agreement with the association of apnea in pathophysiology of SIDS.

Partial arousal deficiency in SIDS victims and noradrenergic neuronal plasticity

Sudden infant death syndrome (SIDS) victims had exhibited during sleep a reduction in cortical arousals despite an increase in subcortical activation. Arousal deficiency in SIDS victims was partial. We could suggest the latent existence of inadequate noradrenergic neuronal plasticity as the background of this partial arousal deficiency of SIDS victims.

The presence of TATA-binding protein in the brainstem, correlated with sleep apnea in SIDS victims

BACKGROUND

Recent reports have indicated that the presence of transcription factors and RNA polymerase decreases in rat brains that suffer perinatal asphyxia from hypoxia. As hypoxia has been proposed as a causative factor in the Sudden Infant Death Syndrome (SIDS), the correlation between TATA-binding protein (TBP) in the brainstem of SIDS victims as a marker of transcription and the incidence of sleep apnea was investigated.

MATERIALS AND METHODS

A total of 38 infants, including 26 cases of SIDS, died under 6 months of age, in a cohort of 27,000 infants studied prospectively to characterize their sleep-wake behavior. The frequency and duration of sleep apnea was analyzed. Brainstem material was collected and immunohistochemistry of TBP was carried out. The density of TBP-positive neurons was measured quantitatively. Correlation analyses were carried out between the density of TBP-positive neurons and the data concerning sleep apnea.

RESULTS

One SIDS-specific positive correlation occurred between the density of TBP-positive neurons in the dorsal raphe nucleus of the midbrain and the duration of central apnea (p=0.049) and two SIDS-specific negative correlations between the density of TBP-positive neurons in the pars compacta and dissipata of the pedunculopontine tegmentum nucleus (PPTNc, PPTNd) in the midbrain and the duration of apnea (p=0.035).

CONCLUSIONS

The significant correlation between the findings of TBP-positive neurons in the midbrain arousal pathway and the characteristics of sleep apnea in SIDS victims is in agreement with the both association of apnea and arousal phenomenon in pathophysiology of SIDS.

Catecholaminergic neurons in the brain-stem and sleep apnea in SIDS victims

BACKGROUND

Tyrosine hydroxylase (TH) is a specific marker for catecholaminergic neurones. Some reports have demonstrated a decrease of TH in the Sudden Infant Death Syndrome (SIDS) compared with controls. To further investigate this, the correlation between TH and sleep apnea was investigated here.

MATERIALS AND METHODS

Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age. They included 26 cases of SIDS. All the infants had been recorded during one night in a pediatric sleep laboratory some 3 to 12 weeks before death. The frequency and the duration of sleep apnea were analyzed. The brain stem material was collected and subjected to immunohistochemical studies for TH. The density of TH-immunoreactive neurons was measured in the nucleus hypoglossus, nervus vagus dorsalis, solitary and ambiguous and the ventrolateral medulla (VLM) in the medulla oblongata. Correlation analyses were carried out between the density of TH-immunoreactive neurons and the data from the sleep apnea studies.

RESULTS

There was no SIDS specific correlation between TH-immunoreactive neurons in the nucleus hypoglossus, nervus vagus dorsalis, solitary and ambiguous and the ventrolateral medulla (VLM) in the medulla oblongata and the frequency and duration of sleep apnea.

CONCLUSIONS

No significant association between the pathological data and the physiological data refers to TH positive neurons in the medulla oblongata in SIDS victims.

Sudden infant deaths: stress, arousal and SIDS

The prevalence of the Sudden Infant Death Syndrome (SIDS) has dropped in most countries following the development of education campaigns on the avoidance of preventable risk factors for SIDS. These include factors in the infant's micro environment, such as prenatal passive smoking, administration of sedative drugs, prone sleep, high ambient temperature or sleeping with the face covered. Sleep laboratory studies have shown that these risk conditions contribute to the development of respiratory and autonomic disorders and reduce the child's arousability. The opposite effects were seen when studying factors protective from SIDS, such as breastfeeding or the use of a pacifier. In victims of SIDS, similar breathing, autonomic and arousal characteristics were recorded days or weeks before their death. It is concluded that in some infants, already immature control mechanisms can be aggravated by environmental factors.

Incomplete arousal processes in infants who were victims of sudden death

Infants who became victims of sudden infant death syndrome (SIDS) aroused less from sleep than control infants. This study was conducted to determine the characteristics of arousal from sleep of infants who eventually died of SIDS. Sixteen infants were monitored some days or weeks before they died of SIDS. Their polygraphic sleep recordings were compared with those of matched control infants. Arousals were scored as subcortical activation (incomplete arousals) or cortical arousal (complete arousals). Cortical arousals were significantly less frequent in the victims who would succumb to SIDS in the future than in the control infants during both REM and non-REM sleep (p = 0.039). The frequency (p = 0.017) and duration (p = 0.005) of subcortical activation were significantly greater in the infants who died of SIDS than in the control infants during REM sleep. Compared with the control infants, the infants who later died of SIDS had more frequent subcortical activation in the first part of the night, between 9:00 P.M. and 12:00 A.M. (p = 0.038), and fewer cortical arousals during the latter part of the night, between 3:00 and 6:00 A.M. (p = 0.011). The present data are suggestive of incomplete arousal processes in infants who eventually died at a time they were presumed to have been asleep.

Investigation into the correlation in SIDS victims between Alzheimer precursor protein A4 in the brainstem and sleep apnea

BACKGROUND

Recently, the appearance of beta-amyloid precursor protein (APP) has been demonstrated in the neonatal brain following hypoxic-ischaemic injury. As chronic hypoxia is one of the favoured theories of causation in the sudden infant death syndrome (SIDS), the correlation between APP in the brainstem and sleep apnea in SIDS was investigated.

MATERIALS AND METHODS

Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age, which included 26 cases of SIDS. All the infants had been recorded during one night in a pediatric sleep laboratory, some 3 to 12 weeks before death. The frequency and duration of sleep apnea were analyzed. The brainstem material was collected and immunohistochemistry with anti-Alzheimer precursor protein A4 (APP) was carried out. The density of APP-positive elements was measured semi-quantitatively. Correlation analyses were carried out between the density of APP-positive elements and the data on sleep apnea.

RESULTS

No correlation was found.

CONCLUSION

No correlation between pathological data of APP and physiological data of sleep apnea was not in agreement with the association of sleep apnea in pathophysiology of SIDS.

The correlation between microtubule-associated protein 2 in the brainstem of SIDS victims and physiological data on sleep apnea

BACKGROUND

Microtubule-associated protein 2(MAP2), a cytoskeletal protein of the neuron, is a marker of early ischemic neuronal damage. As a chronic hypoxic situation exists in the brains of victims of the sudden infant death syndrome (SIDS), the correlation between MAP2-positive neurons or dendritic spines in the brainstem and sleep apnea was investigated in SIDS, which is still the main cause of postneonatal infant death.

MATERIALS AND METHODS

27,000 infants were studied prospectively to characterize their sleep-wake behavior and amongst these, 38 infants died under 6 months of age. They included 26 cases of SIDS. The frequency and duration of sleep apneae were analyzed. The brainstem material was collected and immunohistochemistry of MAP2 was carried out. The density of MAP2-positive neurons, dendrites and dendritic spines were measured quantitatively. Correlation analyses were carried out between the MAP2-associated pathological data and the physiological data of sleep apnea.

RESULTS

One negative correlation between the density of MAP2-positive dendrites in the pars compacta of pedunculo-pontine tegmentum nucleus (PPTNc) and the duration of obstructive apnea (p=0.017) and two SIDS-specific positive correlations between the density of MAP2-positive dendrites in the pars dissipata of pedunculo-pontine tegmentum nucleus (PPTNd) and the duration of central apnea (p=0.005) and between the dorsal raphe and the frequency of obstructive apnea were found in SIDS victims. The density of MAP2-positive dendritic spines in PPTNc was significantly higher in SIDS than in control (p=0.034).

CONCLUSIONS

The significant correlations with the MAP2-positive findings in the midbrain arousal pathway and the characteristics of sleep apnea in SIDS victims were in agreement with the association with apnea and arousal-deficiency in SIDS.

Correlation between the Ki-67 antigen in the brainstem and physiological data on sleep apnea in SIDS victims

BACKGROUND

The Ki-67 antigen appears in all human proliferating cells during late G1, S, M and G2 phases of the cell cycle, but is consistently absent in the Go phase (noncycling) cells. The correlation between Ki-67 in the brainstem and sleep apnea in victims of the sudden infant death syndrome (SIDS) was investigated to elucidate cell kinetics in the brainstem of this condition, which is still the main cause of postneonatal infant death.

MATERIALS AND METHODS

Twenty-six cases of SIDS occurred among 38 infants dying under 6 months of age in a cohort of 27,000 infants studied prospectively to characterize their sleep-wake behavior. All the infants had been recorded during one night in a pediatric sleep laboratory some 3 to 12 weeks before death. The frequency and duration of sleep apnea were analyzed. At autopsy, brainstem material was collected and immunohistochemistry for Ki-67 was carried out. The density of Ki-67-positive neurons was measured semiquantitatively. Correlation analyses were carried out between the density of Ki-67-positive neurons and the data on sleep apnea.

RESULTS

Except in two cases in SIDS victims and in one control, the detection of Ki-67 was negative. No correlation analysis between the Ki-67 and of sleep apnea was found.

CONCLUSIONS

There were no abnormal cell kinetics detected by the demonstration of Ki-67 antigen in the brainstems of SIDS victims.

The correlation between serotonergic neurons in the brainstem and sleep apnea in SIDS victims

BACKGROUND

In the Sudden Infant Death Syndrome (SIDS), a medullary serotonergic network deficiency theory has been proposed, amongst many other hypotheses. The correlation between serotonergic neurons or dendritic spines in the brainstem of SIDS and sleep apnea was investigated here.

MATERIALS AND METHODS

Twenty-seven thousand infants were studied prospectively to characterize their sleep-wake behavior. Of these, 38 infants died under 6 months of age, including 26 cases of SIDS. The frequency and duration of sleep apnea were analyzed. Brainstem material was collected and immunohistochemistry for tryptophan hydroxylase (TrypH) carried out. The density of TrypH-positive neurons was measured quantitatively. Correlation analyses were carried out between the TrypH-associated pathological data and the physiological data of sleep apnea.

RESULTS

One significant positive correlation between the density of TrypH-positive neurons in the dorsal raphe nucleus of the midbrain and the duration of central apnea (p=0.027) was found in SIDS victims.

CONCLUSIONS

Some of serotonergic facts could be involved in the pathophysiology of SIDS.

The correlation between tau protein in the brainstem and sleep apnea in SIDS victims

BACKGROUND

Recently, it has been reported that neuronal plasticity in the brainstem arousal pathway is related to the sudden infant death syndrome (SIDS). Tau protein may contribute to axonal development and neural plasticity; therefore, the correlation between tau protein in the brainstem and sleep apnea in SIDS was investigated here.

MATERIALS AND METHODS

Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age, including 26 cases of SIDS. The frequency and duration of sleep apnea were analyzed on all the infants, having been recorded during one night in a pediatric sleep laboratory some 3-12 weeks before death. The brainstem material was collected and immunohistochemistry of tau was carried out. The density of tau-positive elements was measured semiquantitatively. Correlation analyses were carried out between the density of tau-positive elements and the data of sleep apnea.

RESULTS

In the 26 SIDS cases, tau-positive findings were observed in the sub-pia mater in two cases, in the colloid plexus in one case, in the ependyma and subependyma in five cases, in neurons in two cases and as a general diffusion in one case. In 12 control cases, tau-positive findings were observed in the sub-pia mater in one case and in neuronal elements in three cases. No correlation was found on analysis.

CONCLUSIONS

There was no correlation between the finding of tau in the brainstem of SIDS victims and the incidence of sleep apnea.

Sudden infant deaths: arousal as a survival mechanism

The mechanisms responsible for sudden infant death syndrome (SIDS) are still largely unknown. To explain what factors contribute to the deaths, we suggest a model: the '3 S model for SIDS' that includes 'sicknesses', 'stages of development' and 'surroundings': (1) 'sicknesses' refers to infectious diseases or other medical condition. (2) 'Stages of development' relates to the maturation of vital systems including respiratory, neurovegetative or sleep-wake behavioral controls. (3) 'Surroundings' refers to environmental conditions that enhance the deficiency of cardiorespiratory, vegetative and/or arousal controls. Such conditions were identified by epidemiological studies and include the following main risk factors: the prone body position during sleep, high environmental temperature, maternal smoking or sleep deprivation. An infant could be at higher risk for SIDS because of a deficiency in breathing and cardiac autonomic controls during sleep, inducing repeated episodes of hypoxia and hypoxemia. The risk is increased when the infant has a lower propensity to arouse from sleep and so, to autoresuscitate. The accident has a greater probability to occur when an infection, or an unfavorable environmental factor aggravates the immature cardiorespiratory and sleep/wake behaviors of the infant. The clinical findings could be related to the changes reported in the brainstems of SIDS victims.

Arousal deficiency theory in sudden infant death syndrome with reference to neuronal plasticity

OBJECTIVE

Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age (including 26 infant victims of sudden infant death syndrome (SIDS), five with congenital cardiac abnormalities, two from infected pulmonary dysplasia, two from septic shock with multi-organ failure, one with a prolonged seizure, one from prolonged neonatal hypoxemia and one from meningitis and brain infarction).

METHOD

The frequency and duration of sleep apnea events recorded some 3-12 weeks before the infants' deaths were analyzed. Brainstem material from these 38 infants was studied in an attempt to elucidate the relationship between sleep apnea and neuronal pathological changes in the arousal pathway. The histochemical analyses included Bielschowsky staining and the immunohistochemical analyses included the evaluation of growth-associated phosphoprotein 43 (GAP43) and of synaptophysin as markers for synaptic plasticity. Neurofibrae with positive pathological reactions were quantitatively analyzed. Pathological and physiological data were linked for each infant.

RESULTS

The correlation between sleep apnea and neuronal plasticity in the arousal pathway of the SIDS victims was not seen in the control infants and the correlation between sleep apnea and neuronal plasticity in the arousal pathway found in the control infants was not seen in the SIDS victims.

CONCLUSION

These findings suggest that neuronal plasticity in the brainstem arousal pathway is related with SIDS.

Sudden infant deaths: from epidemiology to physiology

The incidence of sudden infant death syndrome (SIDS) has dropped significantly in most countries following the development of education campaigns on the avoidance of risk factors for SIDS. However, questions have been raised about the physiological mechanism responsible for the effects of these environmental risk factors. Since 1985, a series of prospective, multicentric studies have been developed to address these questions; over 20,000 infants were recorded during one night in a sleep laboratory and among these, 40 infants eventually died of SIDS. In this review, the following methods were employed: sleep recordings and analysis, monitoring procedure, data analysis of sleep stages, cardiorespiratory and oxygen saturation, scoring of arousals, spectral analysis of the heart rate and the determination of arousal thresholds, and statistical analysis and the results including sleep apneas, arousals and heart rate and autonomic controls in both future SIDS victims and normal infants were introduced separately. In addition, the physiological effect of prenatal risk factors (maternal smoking during gestation) and postnatal risk factors (administration of sedative drugs, prone sleeping position, ambient temperature, sleeping with the face covered by a bed sheet, pacifiers and breastfeeding) in normal infants were analyzed. In conclusion, the physiological studies undertaken on the basis of epidemiological findings provide some clues about the physiological mechanisms linked with SIDS. Although the description of the mechanisms responsible for SIDS is still far from complete, it appears to involve both arousal responses and cardiac autonomic controls during sleep-wake processes.

Association between sleep apnea and reactive astrocytes in brainstems of victims of SIDS and in control infants

Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age; 27 infants died from sudden infant death syndrome (SIDS), 5 from congenital cardiac abnormalities, 2 from infected pulmonary dysplasia, 2 from septic shock with multi-organ failure, 1 with a prolonged seizure, and another with prolonged neonatal hypoxemia. The frequency and duration of sleep apneas recorded some 3-12 weeks prior to the infants' death were analyzed. Brainstem material was retrospectively collected from these 33 infants and studied in an attempt to elucidate the relationship between sleep apnea and hypoxic gliosis. The findings were compared between the SIDS victims and the control infants. Brainstem materials were immunohistochemically studied for quantitization of reactive astrocytes using an anti-glial fibrillary acidic protein (GFAP) antibody. The pathological materials were collected within 24h of death. This study focuses on the association between respiratory characteristics and pathology. Physiological and pathological data in the arousal pathway of the brainstem were linked for each infant and variant-covariant analyses were carried out using physiological data as dependent variables and pathological data and categorical data to evaluate the association with SIDS or non-SIDS as independent variables. The study failed to statistically support an association between hypoxic loads, reflected by the GFAP-positive reactive astrocytes in brainstems, the classification of being SIDS or non-SIDS infants, and the characteristics of sleep apnea.

Interaction between apnea, prone sleep position and gliosis in the brainstems of victims of SIDS

Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died suddenly and unexpectedly under 6 months of age. Of these, 26 died from sudden infant death syndrome (SIDS), 5 from congenital cardiac abnormalities, 2 from infected pulmonary dysplasia, 2 from septic shock with multi-organ failure, 1 from a prolonged seizure, 1 from prolonged neonatal hypoxemia, and 1 from meningitis and brain infarction. The frequency and duration of apneas recorded some 3-12 weeks prior to the infants' death were analyzed. The brainstem materials were collected and studied in an attempt to elucidate the relationship between sleep apnea, and prone sleep position and gliosis in some nuclei associated with cardiorespiratory characteristics, such as nucleus ambiguus in the medulla oblongata and the solitary nucleus, as well as structures associated with arousal phenomenon, such as the reticular formation, the superior central nucleus and the nucleus raphe magnus in the pons, the dorsal raphe nuclei in the midbrain and medulla oblongata, periaqueductal gray matter in midbrain, and locus ceruleus. Gliosis was estimated as the density of glial fibrillary acidic protein (GFAP)-positive reactive astrocytes. Variant-covariant analyses were carried out using the characteristics of apnea as an independent variable and sleep position and gliosis as dependent variables. A significant association was found only in the frequency of obstructive apnea and prone position (P<0.001) and gliosis in the raphe nuclei in the midbrain (P<0.001). Although prone position is a well-known risk factor for SIDS, the frequency of obstructive apnea has not been associated with the prone sleep position. The observed relation between prone sleep and the density of gliosis does not relate to epidemiological findings. Further studies are needed to investigate the unexpected statistical association.

From epidemiology to physiology and pathology: apnea and arousal deficient theories in sudden infant death syndrome (SIDS)--with particular reference to hypoxic brainstem gliosis

Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age. They included 26 cases of sudden infant death syndrome (SIDS). Five infants who died from congenital cardiac abnormalities, two from infected pulmonary dysplasia, two from septic shock with multi-organ failure, one during a prolonged seizure, one from a prolonged neonatal hypoxemia, one from meningitis with brain infarction. All the infants had been recorded during one night in a pediatric sleep laboratory some 3-12 weeks before death. The frequency and duration of sleep apneas were analyzed. The infants' brain stem material was collected and immunohistochemistry of glial fibrillary acidic protein (GFAP) was carried out. The density of GFAP-positive reactive astrocytes was measured in the cardiorespiratory and arousal pathway. Akaike information criterion statistics (AIC) were calculated to elucidate the relationship between the epidemiological data on sleep position, the physiological data and the pathological data in SIDS victims. The duration of obstructive apnea was the most significant variable to differentiate between SIDS victims and control infants. In conclusion, the present study sustains the possibility of an organic fragility within the arousal pathway in SIDS victims with repetitive sleep apneas.

From physiology to pathology: arousal deficiency theory in sudden infant death syndrome (SIDS)--with reference to apoptosis and neuronal plasticity

Among 27,000 infants studied prospectively to characterize their sleep-wake behavior, 38 infants died under 6 months of age (including 26 infant victims of sudden infant death syndrome (SIDS), 5 with congenital cardiac abnormalities, 2 from infected pulmonary dysplasia, 2 from septic shock with multi-organ failure, 1 with a prolonged seizure, 1 from prolonged neonatal hypoxemia, 1 from meningitis and brain infarction). The frequency and duration of sleep apneas recorded some 3-12 weeks before the infants' death were analyzed. Brainstem material from these 38 infants was studied in an attempt to elucidate the relationship between sleep apnea and neuronal pathological changes in the arousal pathway. Immunohistochemical analyses included the evaluation of growth-associated phosphoprotein 43 (GAP43) as a marker for synaptic plasticity. The terminal-deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method was used to identify apoptosis. The positive pathological reactions were quantitatively analyzed. The pathological and physiological data were linked for each infant. Akaike Information Criterion (AIC) statistics was calculated to elucidate the relationship between the physiological and the pathological data in the SIDS victims. The findings illustrated the possibility of an organic fragility within the arousal pathway, particularly in the midbrain periaqueductal gray matter, which is associated with the "visceral alerting response". This autonomic response occurs within an acetylcholine afferent system and pedunculopontine tegmental nucleus (PPTN). The finding is, in future SIDS infants, associated with repetitive sleep apnea.

Developmental characteristics of apnea in infants who succumb to sudden infant death syndrome

We compared the breathing characteristics of 40 infants who subsequently died of sudden infant death syndrome (SIDS) with those of 607 healthy infants matched for sex and age. The infants were between 2 and 19 wk old at the time of recording. Compared with the control group, the infants who died of SIDS experienced significantly more frequent episodes of obstructive and mixed sleep apnea. The duration of the apneic episodes did not exceed 15 s. Moreover, the SIDS group had a greater proportion of infants with obstructive and mixed apneic episodes than did the control group. In both groups, the frequency of episodes among male infants with apnea was greater than that among female infants. After the age of 9 wk, the proportion of male infants with episodes of obstructive apnea was greater in the SIDS group than in the control group. The frequency of apneic episodes decreased with age. The rate of decrease was significantly greater in the control subjects than in the SIDS group. This finding was made mainly in male infants. The present study provides further indirect evidence for a slower maturation of respiratory control in some infants who ultimately die of SIDS.

Maternal education and risk factors for sudden death in infants. Working Group of the Groupe Belge de Pédiatres Francophones

To monitor infant care practices associated with risks for sudden infant death, 400 Belgian families with infants less than 6 months old were questioned by 21 paediatricians during routine visits to local paediatric practices and well baby services (11 in urban centres, 10 in rural areas). Because of incomplete information, 35 families were excluded. Of the 365 mothers included in the study, 36.1% had under 7 years of schooling, 38.4% less than 13 years, and 25.5% had a professional school or a university degree. Risk factors for sudden infant death were found in 208 (56.9%) families: a usual non-supine sleep position (31.5% of the infants); sleeping under a duvet (24.1%); mothers smoking during and after gestation (16.4%); a high room temperature (6.6%); use of sedatives (3.8%); necklaces or plastic film in the cot (2.5%); and soft beddings (2.2%). Maternal education, but not the fathers' profession was significantly related to the number of risk factors (mean odds ratio of 4.4; 95% CI: 1.5 to 5.3; P = 0.001). A stepwise logistic regression analysis identified the mother's length of schooling as the single most significant independent factor for the presence of risk (P < 0.005).

CONCLUSION

Less educated mothers reported having been informed of risk-reducing recommendations as frequently as better educated mothers. It can be concluded that future reduction in risks for sudden infant death syndrome should include new strategies designed to modify infant care practices.

Ambient temperature is associated with changes in infants' arousability from sleep

STUDY OBJECTIVE

To evaluate the influence of ambient temperature on infants' arousability from sleep.

DESIGN

Two groups of healthy infants with a median age of 11 weeks were recorded polygraphically during one night: 31 infants were studied at 24 degreesC and 31 infants at 28 degreesC. To determine their arousal thresholds, the infants were exposed to white noises of increasing intensities during REM and NREM sleep. Arousal thresholds were defined by the auditory stimuli needed to induce arousals.

SETTING

N/A.

PATIENTS OR PARTICIPANTS

N/A.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

The arousal thresholds decreased across the night in the infants sleeping at 24 degreesC (p=.017). The finding was not found for the infants sleeping at 28 degreesC. When analyzing the arousal responses according to time of the night, it was found that the auditory thresholds were significantly higher at 28 degreesC than at 24 degreesC between 03:00 hr and 06:00 hr (p=.003). These findings were only seen in REM sleep.

CONCLUSION

High ambient temperature could add to the difficulty to arouse from REM sleep in the late hours of the night.

Reduced arousals following obstructive apneas in infants sleeping prone

A decreased arousability and an increased risk for sudden infant death syndrome (SIDS) have been shown in infants sleeping prone. Obstructive apnea, a known risk factor for SIDS, is less often terminated by an arousal reaction in infants than in adults. The effect of body position on the arousal reaction to spontaneous respiratory events had not been previously studied in infants. The aim of our study was to see if body position has an influence on the frequency and delay of the arousal reaction to obstructive apnea. All obstructive events recorded during two successive nights in 20 infants sleeping one night prone and one night supine were studied. During the supine recording 153 obstructive events were detected, and 217 were detected during the prone session. Prone sleep was not associated with an increased frequency of obstructive apneas. Total sleep time was 382 min (range, 283-456) supine and 423 min (range, 325-521) prone (p = 0.003). Obstructive events duration was 6.5 s (range, 3-21.5) when sleeping supine and 8 s (range, 3.5-30.5) when prone (p = 0.002). Behavioral arousal were found in 57.5 % of obstructive events recorded supine and in 31.3 % of those seen prone (p < 0.001). Arousal occurred after 8 s (range, 0-21) from the start of the obstructions when supine and 10.5 s (range, 3.5-23.5) when prone (p = 0.001). Sighs were found in 34 % of supine obstructive events and in 44.7 % of those prone (p = 0.040). A reaction, i.e. arousal or sigh, was found in 91.5 % of supine events and 76 % of those prone (p < 0.001). We conclude that when sleeping supine, infants arouse to obstructive events more often and after shorter delay than when prone.

Frequency of obstructive and mixed sleep apneas in 1,023 infants

STUDY OBJECTIVES

To collect normative data on the frequency of obstructive and mixed sleep apneas in healthy infants.

STUDY DESIGN

1100 infants were recorded during one night in a sleep laboratory.

SETTING

the recordings were performed in an infant sleep laboratory.

PATIENTS

The recordings of 1023 infants were used for analysis, the data of 77 infants being excluded because of poor recording quality. The infants were born full-term, were healthy at the time of study, had no history of apnea and were aged between 2 and 28 weeks. The polysomnographic recordings were analyzed visually and were subdivided according to the age of the subjects into 2-7 weeks, 8-11 weeks, 12-15 weeks, 16-19 weeks and 20-27 weeks of life.

INTERVENTIONS

NA.

MEASUREMENTS AND RESULTS

At 2-7 weeks of life, obstructive apneas (p=.013) and mixed apneas (p=.004) were significantly more frequent than at any other age group. At 8 to 11 weeks of life, obstructive apneas were significantly more frequent in boys than girls (p=.016).

CONCLUSIONS

The present findings add to our knowledge of infants' respiratory characteristics during sleep.

The influence of a pacifier on infants' arousals from sleep

OBJECTIVE

The risk of sudden infant death during sleep was postulated to decrease with the use of a pacifier and by conditions facilitating arousals from sleep. We evaluated the influence of a pacifier on arousal from sleep in healthy infants.

STUDY DESIGN

Fifty-six healthy infants were studied with polygraphy during 1 night; 36 infants used a pacifier regularly during sleep, and 20 never used a pacifier. Thumb users or occasional pacifier users were not included in the study. The infants were recorded at a median age of 10 weeks (range 6 to 19 weeks). To evaluate auditory arousal thresholds, the infants were exposed to white noise of increasing intensity during rapid eye movement sleep.

RESULTS

Polygraphic arousals occurred at significantly lower auditory stimuli in pacifier users than in nonusers (P =.010). Compared with nonusers, pacifier users were more frequently bottle-fed than breast-fed (P =. 036). Among infants sleeping without a pacifier, breast-fed infants had lower auditory thresholds than bottle-fed infants (P =.049).

CONCLUSIONS

Infants using pacifiers during sleep had lower auditory arousal thresholds than those who did not use a pacifier during sleep. Breast-feeding could be a further factor contributing to lower arousal thresholds. These findings could be relevant to the occurrence of sudden infant deaths during sleep.

Naso-oesophageal probes decrease the frequency of sleep apnoeas in infants

The objective of the study was to determine whether a naso-oesophageal probe modifies sleep and cardiorespiratory patterns in infants with repeated obstructive apnoeas. Two polygraphic recording sessions were conducted in random order for 2 nights on 35 infants suspected to have repeated obstructive sleep apnoeas. One sleep study was performed with a pH probe inserted through the nasal passage down to the distal portion of the oesophagus. The other session was conducted without any naso-oesophageal probe (the baseline study). For the 25 infants who presented repeated obstructive apnoeas during baseline studies, the presence of the probe was associated with a small, but significant, decrease in the number of central apnoeas (median frequency of 18.5 apnoeas per hour without a probe; 16.1 per hour with the probe; P=0.040), and obstructive apnoeas (median of 1.9 apnoeas per hour without a probe; 0.6 per hour with the probe; P=0.016). The presence of the probe was also associated with a small increase in percentage non-rapid eye movement (NREM) sleep frequency. The changes were statistically significant only for infants who had no obstructive apnoea during baseline studies (29 vs. 31%). The presence of a naso-oesophageal probe significantly modifies the infants' respiratory characteristics during sleep. These findings should be considered when reporting and interpreting sleep studies in infants.