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PubMed2006

[The relationship between arousal and nocturnal heart rate variability in patients with obstructive sleep apnea-hypopnea syndrome].

OBJECTIVE: To investigate the relationship between arousal and nocturnal heart rate variability (HRV) in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). METHODS: Twenty-seven patients with moderate to severe OSAHS who underwent overnight polysomnography (PSG) were enrolled, excluding patients with cardiopulmonary and nervous system diseases. An hour continuous PSG monitoring in non-rapid eye movement (NREM) was recorded for all patients. The mean heart rate (HR) in 10 s before each arousal and the peak HR in 10 s after arousal were compared, and the breathing disorder related arousal index (B-ArI) and pulse rate rise index (PRRI) were calculated at this time, and then a correlation analysis was performed. Furthermore, according to minimal oxygen saturation (minSaO(2)), 18 patients with moderate-to-severe OSAHS were matched into 10 events with and without EEG arousal in NREM, and then DeltaHR at apnea termination between these events were compared. RESULTS: The peak HR in 10 s after arousal onset [(81.6 +/- 9.4) beats/min] was significantly higher than the mean HR in 10 s before arousal onset [(69.6 +/- 7.3) beats/min, t = -14.87, P < 0.01], and B-ArI was positively correlated to PRRI (r = 0.97, P < 0.01). The DeltaHR of events with EEG arousal at apnea termination [(11.1 +/- 2.8) beats/min] was higher than those without EEG arousal [(7.0 +/- 2.4) beats/min, t = 4.702, P < 0.01]. CONCLUSIONS: The results indicate that arousal can influence the function of cardiovascular regulation. Frequent arousal is one of the main causes of the cardiovascular consequences in OSAHS patients.

Adult↗
PubMed1985

Hypoxic and hypercapneic arousal responses and prediction of subsequent apnea in apnea of infancy.

Hypoxic and hypercapneic arousal responses from quiet sleep were tested in 56 infants with apnea of infancy (one or more episodes of cyanosis, limpness, and apnea requiring vigorous stimulation or resuscitation with no treatable cause; age 6.8 +/- 1.1 [SEM] months). Responses were compared with those of nine control infants ranging from 1 to 25 months of age. To assess hypercapneic arousal, the inspired PCO2 was rapidly increased during quiet sleep to 60 mm Hg or until arousal (restlessness, agitation, eye opening) occurred. All control infants and those with apnea of infancy aroused to hypercapnea, but control infants aroused at a lower inspired PCO2 (inspired PCO2 40.1 +/- 2.6 mm Hg) than those with apnea of infancy (inspired PCO2 46.9 +/- 1.5 mm Hg, P less than .05). To assess hypoxic arousal, the inspired PO2 was rapidly decreased during quiet sleep to 80 mm Hg or until arousal occurred. All control infants aroused to hypoxia (inspired PO2 78.3 +/- 2.1 mm Hg). However, only 38% of those with apnea of infancy aroused (inspired PO2 78.1 +/- 0.8 mm Hg), indicating an abnormality in recognition of hypoxia, or central brainstem response to hypoxia. During the 10.4 +/- 1.2 months of follow-up, there was a high incidence of subsequent apneas (greater than 20 seconds) during sleep at home in 50 apneic infants. Infants with abnormal hypoxic arousal responses had more severe subsequent apneas than those with normal hypoxic arousal responses (P less than .05).

Arousal↗
PubMed1984

Arousal responses to chemical stimuli during sleep.

Arousal from sleep is an important component of any co-ordinated response to an external stimulus. Respiratory stimuli imposed during sleep are capable of eliciting arousal responses as well as the classic ventilatory responses Considerable survival advantage may result as a consequence of intact arousal mechanisms. Developmental studies of arousal responses to respiratory stimuli are lacking. Arousal responses to chemoreceptor stimuli have been examined in adult tracheotomized dogs, both before and following bilateral surgical denervation of the carotid bodies. Prior to denervation of the carotid bodies arousal in response to isocapnic progressive hypoxia occurred at an arterial oxygen saturation (SaO2) of 83% during slow-wave sleep and 70% in rapid-eye-movement sleep. Airway occlusion induced arousal from Slow-wave-sleep at SaO2 of 88% and from rapid-eye-movement sleep at SaO2 of 84%. Following denervation of the carotid bodies, arousal failed to occur in response to either progressive hypoxia or airway occlusion despite desaturation to 60% in Slow-wave sleep and 50% in rapid-eye-movement-sleep, at which level experiments were arbitrarily terminated. The effect of sleep fragmentation on arousal responses of sleeping dogs to chemoreceptor stimuli has also been studied. A marked impairment of both hypoxic and hypercapnic arousal was produced by sleep fragmentation. The consequences of interfering with arousal mechanisms in experimental animals indicates the considerable potential for similar dysfunction in man to contribute to the pathophysiology of the clinical syndromes of obstructive sleep apnoea and sudden infant death.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Obstruction↗
PubMed2000

Factors influencing the determination of arousal thresholds in infants - a review.

Objective: To review the major confounding factors that influence the determination of arousal thresholds in infants.Review of confounding factors: The determination of arousal thresholds in infants measures their arousability from sleep. The evaluation is influenced by various conditions. The infant's arousability is decreased by maternal factors, such as exposure to cigarette smoke, alcohol, illegal drugs or medications during gestation or breastfeeding. The levels of arousal thresholds also depend on the age of the infant and on experimental conditions, such as previous sleep deprivation, type of arousal challenges, time of administration of the arousal challenge, sleep stage, body position, room temperature, use of a pacifier, bed sharing, or type of feeding. In addition, spontaneous arousals can occur and modify the infant's response to external arousal challenges.Conclusions: Factors known to modify infants' arousability from sleep should be controlled during studies designed to determine arousal thresholds.

Journal Article↗
PubMed1983

Relationship between field strength and arousal response in mice exposed to 60-Hz electric fields.

White-footed mice, Peromyscus leucopus, were exposed to 60-Hz electric fields to study the relationship between field strength and three measures of the transient arousal response previously reported to occur with exposures at 100 kV/m. Five groups of 12 mice each were given a series of four 1-h exposures, separated by an hour, with each group exposed at one of the following field strengths: 75, 50, 35, 25, and 10 kV/m; 8 additional mice were sham-exposed with no voltage applied to the field generator. All mice were experimentally naive before the start of the experiment, and all exposures occurred during the inactive (lights-on) phase of the circadian cycle. The first exposure produced immediate increases in arousal measures, but subsequent exposures had no significant effect on any measure. These arousal responses were defined by significant increases of gross motor activity, carbon dioxide production, and oxygen consumption, and were frequently recorded with field strengths of 50 kV/m or higher. Significant arousal responses rarely occurred with exposures at lower field strengths. Responses of mice exposed at 75 and 50 kV/m were similar to previously described transient arousal responses in mice exposed to 100-kV/m electric fields. Less than half of the mice in each of the field strength groups below 50 kV/m showed arousal responses based on Z (standard) scores, but the arousals of the mice that did respond were similar to those of mice exposed at higher field strengths. Polynomial regression was used to calculate the field strength producing the greatest increases for each of the arousal measures. The results show that the amplitude of the transient arousal response is related to the strength of the electric field, but different measures of arousal may have different relationships to field strength.

Animals↗
PubMed2001

Emotionally arousing pictures increase blood glucose levels and enhance recall.

Arousal enhances memory in human participants and this enhancing effect is likely due to the release of peripheral epinephrine. As epinephrine does not readily enter the brain, one way that peripheral epinephrine may enhance memory is by increasing circulating blood glucose levels. The present study investigated the possibility that emotionally arousing color pictures would improve memory and elevate blood glucose levels in human participants. Blood glucose levels were measured before, 15 min, and 30 min after male university students viewed 60 emotionally arousing or relatively neutral pictures. Participants viewed each picture for 6 s and then had 10 s to rate the arousal (emotional intensity) and valence (pleasantness) of each picture. A free-recall memory test was given 30 min after the last picture was viewed. Although the emotionally arousing and neutral picture sets were given comparable valence ratings, participants who viewed the emotionally arousing pictures rated the pictures as being more arousing, recalled more pictures, and had higher blood glucose levels after viewing the pictures than did participants who viewed the neutral pictures. These findings indicate that emotionally arousing pictures increase blood glucose levels and enhance memory, and that this effect is not due to differences in the degree of pleasantness of the stimuli. These findings support the possibility that increases in circulating blood glucose levels in response to emotional arousal may be part of the biological mechanism that allows emotional arousal to enhance memory.

Adult↗
PubMed2006

Cerebral hemodynamics during arousals in preterm infants.

The aim of the study was to evaluate potential changes of cerebral blood volume (CBV) related to arousals in preterm infants. As arousals are known to change different physiological parameters, it was postulated that this could also hold true for CBV. Polygraphic recordings were performed in 38 preterm infants (18 female, 20 male). The infants' gestational age at birth was 32.0+/-2.3 weeks, postconceptional age was 35.1+/-1.2 weeks and postnatal age at study entry was 24.3+/-2.9 days, birth weight was 1793+/-527 g and actual weight at study entry was 2011+/-324 g [mean (+/- standard deviation)]. CBV was measured using near infrared spectroscopy. Arousals were scored due to the guidelines of the "International Paediatric Work Group on Arousals" and categorized as either cortical (CA) or subcortical arousals (SCA). Altogether, 122 arousals (66 CA, 56 SCA) were scored. According to sleep stage, 77 arousals were analyzed in active sleep, 23 in quiet sleep and 22 in intermediate sleep. Mean duration of arousals was 8.8+/-0.3 s. CBV, cerebral vascular oxygenation and the balance between oxygen delivery and oxygen consumption remained constant during arousals in preterm infants. This was demonstrated for both CA and SCA and was independent of sleep stage, suggesting that the impact of arousals in stable preterm infants is too small to alter cerebral vascular autoregulation.

Arousal↗
PubMed2006

The influence of autonomic arousal and semantic relatedness on memory for emotional words.

Increased memory for emotional stimuli is a well-documented phenomenon. Emotional arousal during the encoding of a stimulus is one mediator of this memory enhancement. Other variables such as semantic relatedness also play a role in the enhanced memory for emotional stimuli, especially for verbal stimuli. Research has not addressed the contributions of emotional arousal, indexed by self-report and autonomic measures, and semantic relatedness on memory performance. Twenty young adults (10 women) were presented neutral-unrelated words, school-related words, moderately arousing emotional words, and highly arousing taboo words while heart rate and skin conductance were measured. Memory was tested with free recall and recognition tests. Results showed that taboo words, which were both semantically related and high arousal were remembered best. School-related words, which were high on semantic relatedness but low on arousal, were remembered better than the moderately arousing emotional words and semantically unrelated neutral words. Psychophysiological responses showed that within the moderately arousing emotional and neutral word groups, those words eliciting greater autonomic activity were better remembered than words that did not elicit such activity. These results demonstrate additive effects of semantic relatedness and emotional arousal on memory. Relatedness confers an advantage to memory (as in the school-words), but the combination of relatedness and arousal (as in the taboo words) results in the best memory performance.

Adolescent↗
PubMed2005

Memory enhancement by a semantically unrelated emotional arousal source induced after learning.

It has been well established that moderate physiological or emotional arousal modulates memory. However, there is some controversy about whether the source of arousal must be semantically related to the information to be remembered. To test this idea, 35 healthy young adult participants learned a list of common nouns and afterward viewed a semantically unrelated, neutral or emotionally arousing videotape. The tape was shown after learning to prevent arousal effects on encoding or attention, instead influencing memory consolidation. Heart rate increase was significantly greater in the arousal group, and negative affect was significantly less reported in the non-arousal group after the video. The arousal group remembered significantly more words than the non-arousal group at both 30 min and 24 h delays, despite comparable group memory performance prior to the arousal manipulation. These results demonstrate that emotional arousal, even from an unrelated source, is capable of modulating memory consolidation. Potential reasons for contradictory findings in some previous studies, such as the timing of "delayed" memory tests, are discussed.

Adult↗
PubMed2005

Postnatal development of ventilatory and arousal responses to hypoxia in human infants.

During the first year of life there is significant maturation of the hypoxic ventilatory response (HVR) in human infants. Compared with adults, healthy term infants have an immature HVR until at least 6 months of age. There are few studies in infants on the effects of sleep state on the HVR but these suggest that at early postnatal ages there is initially no sleep-state related difference; this is followed by a developmental trend towards the adult situation in which the response is depressed in REM sleep compared with NREM. Maternal cigarette smoking is a major risk factor for SIDS and the mechanism for this may involve a depressed HVR in the exposed infant; however studies are limited and the wide variation in cigarette consumption makes interpretation of results difficult. Arousal responses to hypoxia are of vital importance and a failure to arouse has been implicated in SIDS. Sleeping infants frequently fail to arouse in response to hypoxia in QS, whereas in AS they invariably arouse; furthermore arousal latency is longer in QS compared with AS. The oxygen saturation at which infants arouse is not different between sleep states, suggesting that desaturation is more rapid in AS. In QS younger infants arouse more readily than at older ages and arousal is depressed by maternal smoking. These findings suggest that depression of the arousal response to hypoxia in AS may have life-threatening consequences. Infants at increased risk for SIDS have been shown to have both depressed ventilatory and arousal responses to hypoxia, thus they may be at even greater risk.

Animals↗
PubMed2006

CAP, epilepsy and motor events during sleep: the unifying role of arousal.

Arousal systems play a topical neurophysiologic role in protecting and tailoring sleep duration and depth. When they appear in NREM sleep, arousal responses are not limited to a single EEG pattern but are part of a continuous spectrum of EEG modifications ranging from high-voltage slow rhythms to low amplitude fast activities. The hierarchic features of arousal responses are reflected in the phase A subtypes of CAP (cyclic alternating pattern) including both slow arousals (dominated by the <1Hz oscillation) and fast arousals (ASDA arousals). CAP is an infraslow oscillation with a periodicity of 20-40s that participates in the dynamic organization of sleep and in the activation of motor events. Physiologic, paraphysiologic and pathologic motor activities during NREM sleep are always associated with a stereotyped arousal pattern characterized by an initial increase in EEG delta power and heart rate, followed by a progressive activation of faster EEG frequencies. These findings suggest that motor patterns are already written in the brain codes (central pattern generators) embraced with an automatic sequence of EEG-vegetative events, but require a certain degree of activation (arousal) to become visibly apparent. Arousal can appear either spontaneously or be elicited by internal (epileptic burst) or external (noise, respiratory disturbance) stimuli. Whether the outcome is a physiologic movement, a muscle jerk or a major epileptic attack will depend on a number of ongoing factors (sleep stage, delta power, neuro-motor network) but all events share the common trait of arousal-activated phenomena.

Arousal↗
PubMed1982

Arousal responses in near-miss sudden infant death syndrome and in normal infants.

Hypercarbic and hypoxic arousal responses were measured in 22 normal and 11 near-miss sudden infant death syndrome infants during natural sleep. End-tidal PCO2, (PACO2), transcutaneous PO2, electrocardiogram and heart rate, and thoracic and abdominal circumference were continuously recorded. The essential behavioral criteria for arousal were eye opening and crying. For each hypercarbic arousal test, step increases in FICO2 were made until arousal occurred or until PACO2 reached 65 mm Hg. For each hypoxic arousal, step decreases in FIO2 were made until arousal occurred or until FIO2 = 0.15 had been maintained for 20 minutes. The hypercarbic arousal threshold was significantly higher in near-miss SIDS than in normal infants, 54.9 +/- 2.3 vs 48.4 +/- 1.4, respectively ((P less than 0.05). An arousal response to hypoxia occurred in only 9% of near-miss SIDS infants compared to 70% of normal infants (P less than 0.01). The level of respiratory chemostimulation required to produce an arousal response from sleep is significantly greater in near-miss SIDS than in normal infants. We speculate that deficient arousal responsiveness, especially to hypoxia, may prevent potential SIDS victims from responding appropriately to apneic asphyxia.

Arousal↗
PubMed1996

Evaluation of activity-based techniques to identify transient arousal in respiratory sleep disorders.

Daytime sleepiness and impaired cognitive function can be a consequence of recurrent transient arousal from sleep. Arousal is often associated with abrupt changes in the electroencephalogram (EEG), and such changes can be used as an index of sleep disturbance, but EEG analysis is laborious and requires trained observers. Possible alternative indices of arousal not reliant on EEG analysis were investigated. Recordings were made from 36 sleeping subjects who were being investigated for sleep-related breathing disorders. In each study awakenings and transient arousals according to EEG criteria were compared with activity in five potential indirect indicators of arousal: wrist movement, ankle movement, left and right tibial electromyogram, and phase change in ribcage-abdominal movement. The mean values of sensitivity to arousal ranged from only 25 to 45%. However, their high positive predictive accuracies (PPAs, 68 to 92%) indicated that activity, when present, was usually associated with arousal. Sensitivity to awakenings was higher (71-87%), though PPAs were lower (42 to 63%). For the indicator based on ribcage-abdominal phase, the number of periods of activity showed a significant relation to the number of arousals (r = 0.70, P < 0.001). It can be concluded that phase changes in chest/abdomen movement are a useful indicator of arousal associated with obstructive apnoea and related conditions. Limb activity has much lower sensitivity for transient arousal, but may be of value in indicating periods of wakefulness.

Adult↗
PubMed1996

Arousal responses of the newborn piglet to airways obstruction and rebreathing during normothermia and hyperthermia.

Most experimental studies of arousal to respiratory stressors have been performed under neutral thermal conditions. The present study focussed on arousal responses with the added challenge of heat stress. The subjects were two groups of 10 sedated piglets aged 4-6 days and 2-6 days respectively. Respiratory stimuli (partial and total airways obstruction (AO) or rebreathing (RB) expired gases) were applied during non-rapid-eye-movement (NREM) sleep. Measurements of heart rate, SaO2, intra-pleural pressure or inspired CO2 and O2 were recorded during tests in normothermia and hyperthermia. Hyperthermia significantly shortened the time to arousal. Thus, arousal times from partial and total AO and from RB were: in normothermia, 40.3 +/- 5.8, 9.2 +/- 0.7 and 94.9 +/- 14.7 s respectively; in hyperthermia, 17.8 +/- 3.7, 7.6 +/- 0.9 and 68.5 +/- 9.1 s respectively. Cardio-respiratory variables at arousal were similar in both thermal states. Seven non-sedated piglets were challenged with RB stimuli during normothermia only to determine the influence of sleep state on arousal. Arousal in REM sleep was delayed approximately 2-3-fold (NREM, 41.2 +/- 8.2 s; REM, 88.5 +/- 18.1 s), occurring at a lower SaO2 and higher inspired CO2. It is concluded that arousal from NREM sleep under adverse conditions of hyperthermia shortens the arousal time from asphyxial stimuli induced by AO and RB with no change in the arousal threshold.

Airway Obstruction↗
PubMed1997

Arousal and cardiorespiratory responses to airflow obstruction in sleeping lambs: effects of sleep state, age, and repeated obstruction.

We studied the effects of postnatal age on arousal and cardiorespiratory responses to airflow obstruction in sleeping lambs: we also determined the influence of sleep states and repeated airflow obstruction. Sixteen lambs were chronically prepared for monitoring sleep states, arterial O2 saturation (SaO2), heart rate (HR), and intrapleural pressure (Pp1) and were studied from 2-29 days after birth. Obstruction of respiratory airflow by facemask occlusion led to arterial desaturation, augmentation of respiratory efforts, bradycardia, and arousal. Lambs aroused more rapidly and with less desaturation in non-rapid eye movement (NREM) sleep (7 +/- 1 second and 7 +/- 1%, respectively) than in rapid eye movement (REM) sleep (18 +/- 2 seconds and 22 +/- 2%), and cardiac slowing was less in NREM than in REM sleep. In REM sleep only, the arousal latency and desaturation at arousal were affected by postnatal age; arousal responses occurred most rapidly in the youngest (< or = 6 days) and oldest (> or = 13 days) age groups and were delayed at 7-12 days. Repeated episodes of airflow obstruction led to reduced arousability in REM sleep only. We conclude that arousal from REM. but not NREM, sleep in response to the obstruction of respiratory airflow is transiently depressed during early postnatal development and that repeated obstructions and arousals also lead to depressed arousal from REM sleep.

Age Factors↗
PubMed2004

Reliability of scoring arousals in normal children and children with obstructive sleep apnea syndrome.

STUDY OBJECTIVES: Scoring of arousals in children is based on an extension of adult criteria, as defined by the American Sleep Disorders Association (ASDA). By this, a minimum duration of 3 seconds is required. A few recent studies utilized modified criteria for the study of children, with durations as short as 1 second. However, the validity and reliability of scoring these shorter arousals have never been verified. Based on studies in adults, we hypothesized that interscorer agreement for scoring arousals shorter than 3 seconds was poor. DESIGN: Retrospective review of polysomnograms by 2 experienced sleep practitioners who independently scored arousals according to the ASDA 3-second criteria and modified duration criteria of 1 and 2 seconds. SETTING: Academic hospital. PATIENTS OR PARTICIPANTS: 20 polysomnographic studies from children aged 3 to 8 years with mild to severe obstructive sleep apnea syndrome, and 16 polysomnographic studies from normal children. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: The intraclass correlation coefficient for scoring ASDA arousals was 0.90 (95% confidence interval: 0.81-0.95), indicating excellent interscorer agreement. The intraclass correlation coefficient for scoring modified 1-second and 2-second arousals were 0.35 (95% confidence interval: 0.02-0.61) and 0.42 (95% confidence interval: 0.12-0.65) respectively, indicating poor to fair interscorer agreement. Furthermore, modified 1-second and 2-second arousals accounted for less than 15% of all arousals scored. CONCLUSIONS: We conclude that there is much poorer interscorer agreement for scoring arousals shorter than 3 seconds, when compared to the standard ASDA criteria. We propose that scoring of arousals in children should follow the standard ASDA criteria.

Arousal↗
PubMed2006

Effects of sleep fragmentation on the arousability to resistive loading in NREM and REM sleep in normal men.

STUDY OBJECTIVE: In healthy subjects, arousability to inspiratory resistive loading is greater during rapid eye movement (REM) sleep compared with non-REM (NREM) sleep but is poorest in REM sleep in patients with sleep apnea. We therefore examined the hypothesis that sleep fragmentation impairs arousability, especially from REM sleep. DESIGN: Two blocks of 3 polysomnographies (separated by at least 1 week) were performed randomly. An inspiratory-loaded night followed either 2 undisturbed control nights (LN(C)) or 2 acoustically fragmented nights (LN(F)) SETTING: Sleep laboratory. PARTICIPANTS: Sixteen healthy men aged 20 to 29 years. INTERVENTIONS: In both loaded nights, an inspiratory resistive load was added via a valved facemask every 2 minutes during sleep and turned off either when arousal occurred or after 2 minutes. MEASUREMENTS AND RESULTS: During LN(F), arousability remained significantly greater in REM sleep (71% aroused within 2 minutes) compared with stage 2 (29%) or stage 3/4 (16%) sleep. After sleep fragmentation, arousability was decreased in stage 2 sleep (LN(F): 29%; LN(C): 38%; p < .05) and low in early REM sleep, increasing across the night (p < .01). In stage 3/4 sleep, neither an attenuation nor a change across the night was seen after sleep fragmentation. CONCLUSIONS: Mild sleep fragmentation is already sufficient to attenuate arousability in stage 2 sleep and to decrease arousability in early, compared with late, REM sleep. This means that sleep fragmentation affects the arousal response to increasing resistance and that the effects are different in stage 2 and REM sleep. The biologic reason for this increase in the arousal response in REM sleep across the night is not clear.

Adult↗
PubMed1997

Development of cardiopulmonary integration and the role of arousability from sleep.

The recent literature on cardiopulmonary integration in infants is surveyed here, focusing on arousals from sleep. Recent studies reported that the ontogenicity of cardiopulmonary integration cannot be evaluated independently from that of sleep-wake cycles. The issue is of importance for researchers and clinicians evaluating cardiorespiratory characteristics in infants. It also has significant implications in the understanding of clinical conditions, such as parasomnias, obstructive sleep apneas, or some cases of sudden infant death syndrome. The propensity to arouse can be evaluated by exposing the sleeper to awakening challenges. Arousal thresholds are determined by measuring the intensity of the stimulus needed to induce arousals. However, these studies are complicated by factors such as the scoring of the arousal responses. Another difficulty lies in the choice and modality of the arousal stimulus. Noise, gases, light, and nociceptive, mechanical, chemical, or temperature stimuli have all been used to induce arousals. Confounding factors modify the sleeper's responses to a given stimulus. Prenatal drug, alcohol, or cigarette use and the infant's age or, previous sleep deprivation also modify thresholds. Other confounding factors include time of the night, sleep stages, the sleeper's body position, and sleeping conditions. Arousal can also occur spontaneously because of endogenous stimuli. The literature surveyed here also covers such unresolved issues as the clinical significance of aborted arousals, or the mechanisms responsible for the arousal reactions.

Age Factors↗