Proposed supplements and amendments to 'A Manual of Standardized Terminology, Techniques and Scoring System for Sleep Stages of Human Subjects', the Rechtschaffen & Kales (1968) standard

Nasal CPAP reduces systemic blood pressure in patients with obstructive sleep apnoea and mild sleepiness

BACKGROUND

A randomised controlled study was undertaken to examine the effect of nasal continuous positive airway pressure (CPAP) on 24 hour systemic blood pressure (BP) in patients with obstructive sleep apnoea (OSA).

METHODS

Patients were fitted with an ambulatory BP measuring device as outpatients during normal activities and recorded for 24 hours before starting therapeutic or subtherapeutic (4 cm H(2)O) CPAP treatment. BP monitoring was repeated before completion of 12 weeks of treatment. The primary end point was the change in 24 hour mean BP.

RESULTS

Twenty three of 28 participants in each treatment arm completed the study. There was no significant difference between the two groups in age, body mass index, Epworth Sleepiness Score, apnoea-hypopnoea index, arousal index, and minimum Sao(2). Twenty four patients were hypertensive. The pressure in the therapeutic CPAP group was 10.7 (0.4) cm H(2)O. CPAP usage was 5.1 (0.4) and 2.6 (0.4) hours/night for the therapeutic and subtherapeutic CPAP groups, respectively (p<0.001). After 12 weeks of treatment there were significant differences between the two CPAP groups in mean (SE) changes in 24 hour diastolic BP (-2.4 (1.2) v 1.1 (1.0) mm Hg (95% CI -6.6 to -0.5), p = 0.025); 24 hour mean BP (-2.5 (1.3) v 1.3 (1.1) mm Hg (95% CI -7.2 to -0.2), p = 0.037); sleep time systolic BP (-4.1 (2.1) v 2.2 (1.8) mm Hg (95% CI -11.8 to -0.7), p = 0.028); and sleep time mean BP (-3.6 (1.7) v 1.3 (1.4) mm Hg (95% CI -9.2 to -0.4), p = 0.033).

CONCLUSIONS

Compared with subtherapeutic CPAP, 12 weeks of treatment with therapeutic CPAP leads to reductions in 24 hour mean and diastolic BP by 3.8 mm Hg and 3.5 mm Hg, respectively, in mildly sleepy patients with OSA.

Perception of sleep in recovering alcohol-dependent patients with insomnia: relationship with future drinking

BACKGROUND

Subjective and objective measures of poor sleep in alcoholic insomniacs predict relapse to drinking. Nonalcoholic insomniacs underestimate their total sleep time (TST) and overestimate their sleep onset latency (SOL) and wake time after sleep onset (WASO) compared with polysomnography (PSG). This study evaluated 3 hypotheses: (1) subjective SOL would predict frequency of future drinking; (2) participants would overestimate SOL and WASO and underestimate TST; and (3) higher amounts of over- and underestimates of sleep at baseline would predict worse drinking outcomes prospectively.

METHODS

Participants (N=18), mean age 44.6 years (+/-13.2), underwent an adaptation night and then 2 nights of PSG 3 weeks apart. They also provided morning estimates of SOL, WASO, TST, and sleep efficiency (SE). Following the baseline PSG, participants were followed over 12 weeks. A 2-way ANOVA (night x method of measuring sleep) compared results and regression analyses predicted drinking. Drinking outcomes were defined as number of days drinking (DD) and number of heavy-drinking days (HDD) during 2 consecutive 6-week follow-up periods.

RESULTS

Most participants (72%) overestimated SOL by a mean of 21.3 (+/-36) minutes compared with PSG [F(1, 14)=7.1, p<0.03]. Unexpectedly, 89% underestimated WASO by a mean difference of 48.7 (+/-49) minutes [F(1, 14)=15.6, p<0.01]. Drinking during the first 6-week study period was predicted by both subjective estimates of WASO and their accuracy, whereas drinking during the second 6-week period was predicted by both subjective estimations of sleep and rapid eye movement sleep latency.

CONCLUSION

Greater subjective accuracy of wakefulness at night provided by the patient predicted drinking during the study. Unlike nonalcoholic insomniacs, this alcoholic sample significantly underestimated WASO compared with PSG values. The predictive ability of sleep parameters depended on the selected measure of drinking outcomes and when outcomes were measured. Subjective sleep measures were better predictors of future drinking than corresponding PSG measures.

The adolescent decline of NREM delta, an indicator of brain maturation, is linked to age and sex but not to pubertal stage

Two dramatic phenomena of human adolescence are sexual maturation and a steep decline in the delta EEG of non-rapid eye movement (NREM) sleep. It has long been speculated that these developmental changes are causally related. Here, we present the first longitudinal data on this issue. Cohorts of 9- and 12-year-old children (n = 31, 38) were studied with in-home sleep EEG recordings at 6-mo intervals over 2 years. Pubertal (Tanner) stage, height, and weight were obtained at each time point. NREM delta power density (DPD) did not change significantly over ages 9-11 years, and its level did not differ in boys and girls. DPD declined by 25% between ages 12 and 14 years. This decline was parallel in the two sexes, but levels were lower in girls, suggesting that their DPD decline began earlier. Mixed effect analyses demonstrated that DPD was strongly related to age with Tanner stage, height, weight and body mass index controlled but that none of these measures of physical and sexual development was related to DPD with age controlled. NREM delta is the sleep EEG component homeostatically related to prior waking duration and the intensity of waking brain activity. We hypothesize that the DPD decline is caused by age-programmed synaptic pruning that decreases waking brain metabolic rate. This reduced rate would decrease the "substrate" for delta homeostasis. Whether or not this interpretation proves correct, these longitudinal data demonstrate that the delta decline in adolescence reflects brain processes that are not predicted by physical growth or sexual maturation.

Self-awakening, sleep inertia, and P3 amplitude in elderly people

It is well known that sleepiness is sometimes experienced in the afternoon. A short afternoon nap is thought to be effective in reducing sleepiness. However, sleep inertia occurs even after a short nap, and this could be a major risk factor for injuries from falling by the elderly. In the present study, the effect of self-awakening on sleep inertia after a 20-min. nap was examined. Nine participants (M=74.1 yr., SD=5.0 yr.) took part in the three experimental conditions: the self-awakened nap, the forced-awakened nap, and the control (no-nap) conditon. Analysis showed sleepiness and performance after the nap significantly improved compared with the control condition. P3 amplitude tended to be larger after self-awakening than after forced-awakening. The present study indicates a 20-min. nap reduces afternoon sleepiness, and the application of self-awakening may contribute to higher arousal after a nap taken by this elderly group.

The "ways" we look at dreams: evidence from unilateral spatial neglect (with an evolutionary account of dream bizarreness)

Despite decades of research, the question of whether the rapid eye movements (REMs) of paradoxical sleep (PS) are equivalent to waking saccades and whether their direction is congruent with visual spatial events in the dream scene is still very controversial. We gained an insight into these questions through the study of a right brain damaged patient suffering attentional neglect for the left side of space and drop of the optokinetic nystagmus (OKN) with alternating rightward slow/leftward fast phases evoked by rightward optic flow. During PS the patient had frequent Nystagmoid REMs with alternating leftward slow/rightward fast phases and reported dreams with visual events evoking corresponding OKN such as a train running leftward. By contrast, just as in waking OKN, Nystagmoid REMs with alternating rightward slow/leftward fast phases were virtually absent. REMs followed by staring eye position or by consecutive REMs were also observed: these showed no asymmetry comparable to that of Nystagmoid ones. The selective disappearance of Nystagmoid REMs in one horizontal direction proves, for the first time, that in humans different types of REMs exists and that these are driven by different premotor mechanisms. Concomitant drop of OKN and Nystagmoid REMs toward the same horizontal direction demonstrates that phylogenetically ancient oculomotor mechanisms, such as the OKN, are shared by waking and PS. On this evidence and converging findings from animal, neuropsychological and brain imaging studies, a new evolutionary account of dream bizarreness is proposed. Classification and labelling of the different types of REMs are also provided.

Adenosinergic mechanisms contribute to individual differences in sleep deprivation-induced changes in neurobehavioral function and brain rhythmic activity

Large individual differences characterize the changes induced by sleep deprivation on neurobehavioral functions and rhythmic brain activity. To investigate adenosinergic mechanisms in these differences, we studied the effects of prolonged waking and the adenosine receptor antagonist caffeine on sustained vigilant attention and regional electroencephalogram (EEG) power in the ranges of theta activity (6.25-8.25 Hz) in waking and the slow oscillation (<1 Hz) in sleep. Activity in these frequencies is functionally related to sleep deprivation. In 12 subjectively caffeine-sensitive and 10 -insensitive young men, psychomotor vigilance task (PVT) performance and EEG were assessed at 3 h intervals before, during, and after one night without sleep. After 11 and 23 h waking, subjects received 200 mg caffeine and placebo in double-blind, cross-over manner. In the placebo condition, sleep deprivation impaired PVT speed more in caffeine-sensitive than in caffeine-insensitive men. This difference was counteracted by caffeine. Theta power in waking increased more in a frontal EEG derivation than in a posterior derivation. Caffeine attenuated this power gradient in caffeine sensitive subjects. Sleep loss also differently affected the power distribution <1 Hz in non-rapid eye movement sleep between caffeine sensitive and insensitive subjects. Also, this difference was mirrored by the action of caffeine. The effects of sleep deprivation and caffeine on sustained attention and regional EEG power in waking and sleep were inversely related. These findings suggest that adenosinergic mechanisms contribute to individual differences in waking-induced impairment of neurobehavioral performance and functional aspects of EEG topography associated with sleep deprivation.

Increased cerebral blood flow velocity in children with mild sleep-disordered breathing: a possible association with abnormal neuropsychological function

OBJECTIVE

Sleep-disordered breathing describes a spectrum of upper airway obstruction in sleep from simple primary snoring, estimated to affect 10% of preschool children, to the syndrome of obstructive sleep apnea. Emerging evidence has challenged previous assumptions that primary snoring is benign. A recent report identified reduced attention and higher levels of social problems and anxiety/depressive symptoms in snoring children compared with controls. Uncertainty persists regarding clinical thresholds for medical or surgical intervention in sleep-disordered breathing, underlining the need to better understand the pathophysiology of this condition. Adults with sleep-disordered breathing have an increased risk of cerebrovascular disease independent of atherosclerotic risk factors. There has been little focus on cerebrovascular function in children with sleep-disordered breathing, although this would seem an important line of investigation, because studies have identified abnormalities of the systemic vasculature. Raised cerebral blood flow velocities on transcranial Doppler, compatible with raised blood flow and/or vascular narrowing, are associated with neuropsychological deficits in children with sickle cell disease, a condition in which sleep-disordered breathing is common. We hypothesized that there would be cerebral blood flow velocity differences in sleep-disordered breathing children without sickle cell disease that might contribute to the association with neuropsychological deficits.

DESIGN

Thirty-one snoring children aged 3 to 7 years were recruited from adenotonsillectomy waiting lists, and 17 control children were identified through a local Sunday school or as siblings of cases. Children with craniofacial abnormalities, neuromuscular disorders, moderate or severe learning disabilities, chronic respiratory/cardiac conditions, or allergic rhinitis were excluded. Severity of sleep-disordered breathing in snoring children was categorized by attended polysomnography. Weight, height, and head circumference were measured in all of the children. BMI and occipitofrontal circumference z scores were computed. Resting systolic and diastolic blood pressure were obtained. Both sleep-disordered breathing children and the age- and BMI-similar controls were assessed using the Behavior Rating Inventory of Executive Function (BRIEF), Neuropsychological Test Battery for Children (NEPSY) visual attention and visuomotor integration, and IQ assessment (Wechsler Preschool and Primary Scale of Intelligence Version III). Transcranial Doppler was performed using a TL2-64b 2-MHz pulsed Doppler device between 2 pm and 7 pm in all of the patients and the majority of controls while awake. Time-averaged mean of the maximal cerebral blood flow velocities was measured in the left and right middle cerebral artery and the higher used for analysis.

RESULTS

Twenty-one snoring children had an apnea/hypopnea index <5, consistent with mild sleep-disordered breathing below the conventional threshold for surgical intervention. Compared with 17 nonsnoring controls, these children had significantly raised middle cerebral artery blood flow velocities. There was no correlation between cerebral blood flow velocities and BMI or systolic or diastolic blood pressure indices. Exploratory analyses did not reveal any significant associations with apnea/hypopnea index, apnea index, hypopnea index, mean pulse oxygen saturation, lowest pulse oxygen saturation, accumulated time at pulse oxygen saturation <90%, or respiratory arousals when examined in separate bivariate correlations or in aggregate when entered simultaneously. Similarly, there was no significant association between cerebral blood flow velocities and parental estimation of child's exposure to sleep-disordered breathing. However, it is important to note that whereas the sleep-disordered breathing group did not exhibit significant hypoxia at the time of study, it was unclear to what extent this may have been a feature of their sleep-disordered breathing in the past. IQ measures were in the average range and comparable between groups. Measures of processing speed and visual attention were significantly lower in sleep-disordered breathing children compared with controls, although within the average range. There were similar group differences in parental-reported executive function behavior. Although there were no direct correlations, adjusting for cerebral blood flow velocities eliminated significant group differences between processing speed and visual attention and decreased the significance of differences in Behavior Rating Inventory of Executive Function scores, suggesting that cerebral hemodynamic factors contribute to the relationship between mild sleep-disordered breathing and these outcome measures.

CONCLUSIONS

Cerebral blood flow velocities measured by noninvasive transcranial Doppler provide evidence for increased cerebral blood flow and/or vascular narrowing in childhood sleep-disordered breathing; the relationship with neuropsychological deficits requires further exploration. A number of physiologic changes might alter cerebral blood flow and/or vessel diameter and, therefore, affect cerebral blood flow velocities. We were able to explore potential confounding influences of obesity and hypertension, neither of which explained our findings. Second, although cerebral blood flow velocities increase with increasing partial pressure of carbon dioxide and hypoxia, it is unlikely that the observed differences could be accounted for by arterial blood gas tensions, because all of the children in the study were healthy, with no cardiorespiratory disease, other than sleep-disordered breathing in the snoring group. Although arterial partial pressure of oxygen and partial pressure of carbon dioxide were not monitored during cerebral blood flow velocity measurement, assessment was undertaken during the afternoon/early evening when the child was awake, and all of the sleep-disordered breathing children had normal resting oxyhemoglobin saturation at the outset of their subsequent sleep studies that day. Finally, there is an inverse linear relationship between cerebral blood flow and hematocrit in adults, and it is known that iron-deficient erythropoiesis is associated with chronic infection, such as recurrent tonsillitis, a clinical feature of many of the snoring children in the study. Preoperative full blood counts were not performed routinely in these children, and, therefore, it was not possible to exclude anemia as a cause of increased cerebral blood flow velocity in the sleep-disordered breathing group. However, hemoglobin levels were obtained in 4 children, 2 of whom had borderline low levels (10.9 and 10.2 g/dL). Although there was no apparent relationship with cerebral blood flow velocity in these children (cerebral blood flow velocity values of 131 and 130 cm/second compared with 130 and 137 cm/second in the 2 children with normal hemoglobin levels), this requires verification. It is of particular interest that our data suggest a relationship among snoring, increased cerebral blood flow velocities and indices of cognition (processing speed and visual attention) and perhaps behavioral (Behavior Rating Inventory of Executive Function) function. This finding is preliminary: a causal relationship is not established, and the physiologic mechanisms underlying such a relationship are not clear. Prospective studies that quantify cumulative exposure to the physiologic consequences of sleep-disordered breathing, such as hypoxia, would be informative.

Stress-related sleep disturbance and polysomnographic response to caffeine

BACKGROUND AND PURPOSE

To determine the sleep response to caffeine in individuals vulnerable to stress-related sleep disturbance as measured by polysomnography.

PATIENTS AND METHODS

Eleven healthy individuals without insomnia scoring low (4 women, mean age=32.64+/-15.46 years) and 10 healthy individuals also without insomnia scoring high (6 women, mean age=34.20+/-13.73 years) on a measure of vulnerability to stress-related sleep disturbance were studied in a laboratory protocol. A moderate-low dose of caffeine (3 mg/kg) was administered 1h prior to lights-out and compared to a counterbalanced control night with each condition separated by 1 week. Standard polysomnographic measures were assessed (i.e. total sleep time, sleep efficiency, latency to persistent sleep, and sleep stage percentages) for both control and caffeine nights.

RESULTS

There were no between-group differences in sleep on the control night. Importantly, individuals reporting vulnerability to stress-related sleep disturbance had significantly prolonged latency to persistent sleep in response to the caffeine challenge (interaction; P<0.05).

CONCLUSION

Normal sleepers with an identified vulnerability to stress-induced sleep disturbance exhibited greater objectively verifiable sleep-reactivity in response to a caffeine challenge compared to non-vulnerable individuals. These results suggest that the construct of individual differences in vulnerability to sleep disturbance applies to a pharmacological 'stressor' (i.e. caffeine) as well as to previously assessed stressors such as a first-night effect. This finding provides further support for generalized trait vulnerability by demonstrating a sleep disturbance to a wake-promoting pharmacological challenge in specific a priori identified individuals.

Vigilance, alertness, or sustained attention: physiological basis and measurement

Vigilance is a term with varied definitions but the most common usage is sustained attention or tonic alertness. This usage of vigilance implies both the degree of arousal on the sleep-wake axis and the level of cognitive performance. There are many interacting neural and neurotransmitter systems that affect vigilance. Most studies of vigilance have relied on states where the sleep-wake state is altered, e.g. drowsiness, sleep-deprivation, and CNS-active drugs, but there are factors ranging from psychophysics to motivation that may impact vigilance. While EEG is the most commonly studied physiologic measure of vigilance, various measures of eye movement and of autonomic nervous system activity have also been used. This review paper discusses the underlying neural basis of vigilance and its assessment using physiologic tools. Since, assessment of vigilance requires assessment of cognitive function this aspect is also discussed.

Follow-up assessment of CPAP efficacy in patients with obstructive sleep apnea using an ambulatory device based on peripheral arterial tonometry

This study aimed to assess the accuracy of a wrist-worn device based on peripheral arterial tonometry (Watch_PAT 100) to detect residual episodes of respiratory disturbance during continuous positive airway pressure (CPAP) therapy. Concurrent polysomnography was used as the reference standard to identify sleep disordered breathing (SDB) events. The study was conducted in three sleep laboratories affiliated with tertiary care academic medical centers. Seventy patients using CPAP to treat obstructive sleep apnea for at least 3 months, following an in-laboratory titration to determine the optimal therapeutic positive airway pressure, participated in this study. Symptoms indicating suboptimal therapy were not required for participation, but self-reported adherence to CPAP therapy was necessary for inclusion. Interventions are not applicable in this study. The accuracy of the PAT-derived respiratory disturbance index (PAT RDI scored by automated algorithm) to detect residual SDB on CPAP was assessed against polysomnography (PSG) using Bland-Altman analysis, receiver-operator characteristic (ROC) curves, and likelihood ratios for increasing (LR+) and decreasing (LR-) the probability of moderate-severe SDB in the study population. Respiratory events on the PSG were quantified using standard criteria for research investigations ("Chicago criteria") to yield a PSG RDI.C. Based on the PSG results, 19% of the participants had moderate-severe SDB (PSG RDI.C>15 events per hour) on their prescribed pressure. For PAT RDI >15 events per hour, the area under the ROC curve was 0.95 (SE 0.03, p < 0.0001, 95% CI 0.89 to 1.00), the LR+ was 8.04 (95% CI 3.64-17.7), and the LR- was 0.17 (95% CI 0.05-0.62). The mean difference between the PAT RDI and PSG RDI.C was three (2SD 14.5) events per hour. Therefore, residual moderate-severe SDB on CPAP was not uncommon in a multicenter population self-reporting adherence to CPAP therapy to treat obstructive sleep apnea. The Watch_PAT device accurately identified participants with moderate-severe SDB while using CPAP in the attended setting of a sleep laboratory.

Follow-up on metabolic markers in children treated for obstructive sleep apnea

RATIONALE

In adults, obstructive sleep apnea (OSA) is associated with metabolic dysfunction that improves with treatment of OSA. No equivalent studies exist in children.

OBJECTIVE

To examine the relationship between metabolic markers and OSA with time and treatment in children.

METHODS

Metabolic markers measured on a fasting morning blood sample at diagnostic polysomnography and follow-up 1.3 +/- 0.6 yr later.

MEASUREMENTS AND MAIN RESULTS

Forty-five children (34 males), aged 6.9 +/- 3.5 yr, and including 12 obese subjects, were in the final analysis. There were no differences in metabolic markers between children with and without OSA at initial study; however, obese children had significantly higher insulin (106.1 +/- 72.1 vs. 66.7 +/- 37.6 pmol/L; p = 0.028), insulin/glucose ratio (23.7 +/- 14.3 vs. 14.7 +/- 8.0; p = 0.02), and significantly lower high-density lipoprotein cholesterol (1.3 +/- 0.2 vs. 1.6 +/- 0.4 nmol/L; p = 0.005) than nonobese children. Twenty children underwent surgical removal of adenotonsillar tissue, whereas 12 children with OSA elected not to have treatment. OSA persisted after treatment in five children, and resolved in 27. Thirteen children did not have OSA on initial or follow-up studies. At follow-up, there was a small but significant improvement in total cholesterol in those children whose OSA was resolved (4.8 +/- 0.8 to 4.7 +/- 0.6 nmol/L; p = 0.005) and a trend for obese children with persisting OSA to have elevated insulin levels compared with obese children without OSA (p = 0.07).

CONCLUSION

Obesity appears to be the major influence on metabolic dysfunction in children with OSA, but these preliminary data also suggest that resolution or persistence of OSA may affect changes in metabolic function over time.

Non-arteritic anterior ischaemic optic neuropathy is nearly systematically associated with obstructive sleep apnoea

AIM

To evaluate newly diagnosed non-arteritic anterior ischaemic optic neuropathy (NAION) patients for the existence of an associated sleep apnoea syndrome.

METHODS

Newly identified NAION patient underwent polysomnography. The prevalence of sleep apnoea in NAION patients was compared to the prevalence previously found in the general population. Hypertension, diabetes, hyperlipidaemia, and atheromatous lesions of carotid vessels as classic risk factors associated with NAION were also identified.

RESULTS

27 consecutive newly diagnosed NAION patients (18 men and nine women, mean age 65 (SD 8) years, body mass index 27.2 (3.8) kg/m2) were included in the study. 24 of these 27 NAION patients (89%) exhibited a sleep apnoea syndrome (respiratory disturbance index: 37.2/h (SD 18.3/h). Risk ratio for a NAION patient to have sleep apnoea was 4.9 compared to the general population (p < 0.001). Sleep apnoea was 1.5-2-fold more frequent than the rate of the other identified risk factors typically associated with NAION (hypertension, diabetes).

CONCLUSIONS

Sleep apnoea is the most frequent disorder associated with NAION and should be screened in this population. At least a questionnaire related to obstructive sleep apnoea symptoms and assessment of sleepiness should be systematically proposed to patients with NAION.

Effect of cabergoline added to levodopa treatment on sleep-wake cycle in idiopathic Parkinson's disease: an open label 24-hour polysomnographic study

Few studies focused on the effects of cabergoline on sleep-wake cycle in PD. Twelve patients affected by PD treated with levodopa as monotherapy underwent two 24-hour ambulatory polysomnographic (A-PSG) sessions twice: in baseline condition (levodopa as monotherapy) and after addition of cabergoline. In each condition, a subjective evaluation of sleep quality and daytime sleepiness was obtained by means of Parkinson's disease Sleep Scale (PDSS) and the Epworth Sleepiness Scale. The statistical analysis of sleep parameters revealed a significant increase of sleep efficiency and slow wave sleep under cabergoline. The PDSS total score showed a significant improvement of overall sleep quality after cabergoline. No significant changes in daytime sleepiness were observed. No patient referred and/or showed sleep attacks before and after addition of cabergoline. We hypothesize that the long-lasting effect of cabergoline may improve the objective quality of nocturnal sleep in PD patients complaining nocturnal motor disability without inducing daytime sleepiness.

[Sleep-related breathing disorders. Sleep anamnesis questionnaire and determination of clinical results within the framework of staged diagnostics]

Sleep-related breathing disorders (SBAS) affect approximately 8% of the population of middle aged adults. At the age of 20 years, approximately 10% of the population snore, while at the age of 60 about 50% of men snore. Some 9% of middle aged women and 24% of middle aged men have an apnea hypopnea index (AHI) of >5 (number of nocturnal apnea and hypopnea per hour of sleep). Sleep apnea hypopnea syndrome is found in 2% of the women and 4% of the men, i.e. they have an AHI>5 associated with daytime sleepiness. Forms, check lists, summaries and patient-readable questionnaires have proved helpful in the evaluation of SBAS.

Sleep-disordered breathing, behavior, and cognition in children before and after adenotonsillectomy

OBJECTIVES

Most children with sleep-disordered breathing (SDB) have mild-to-moderate forms, for which neurobehavioral complications are believed to be the most important adverse outcomes. To improve understanding of this morbidity, its long-term response to adenotonsillectomy, and its relationship to polysomnographic measures, we studied a series of children before and after clinically indicated adenotonsillectomy or unrelated surgical care.

METHODS

We recorded sleep and assessed behavioral, cognitive, and psychiatric morbidity in 105 children 5.0 to 12.9 years old: 78 were scheduled for clinically indicated adenotonsillectomy, usually for suspected SDB, and 27 for unrelated surgical care. One year later, we repeated all assessments in 100 of these children.

RESULTS

Subjects who had an adenotonsillectomy, in comparison to controls, were more hyperactive on well-validated parent rating scales, inattentive on cognitive testing, sleepy on the Multiple Sleep Latency Test, and likely to have attention-deficit/hyperactivity disorder (as defined by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition) as judged by a child psychiatrist. In contrast, 1 year later, the 2 groups showed no significant differences in the same measures. Subjects who had an adenotonsillectomy had improved substantially in all measures, and control subjects improved in none. However, polysomnographic assessment of baseline SDB and its subsequent amelioration did not clearly predict either baseline neurobehavioral morbidity or improvement in any area other than sleepiness.

CONCLUSIONS

Children scheduled for adenotonsillectomy often have mild-to-moderate SDB and significant neurobehavioral morbidity, including hyperactivity, inattention, attention-deficit/hyperactivity disorder, and excessive daytime sleepiness, all of which tend to improve by 1 year after surgery. However, the lack of better correspondence between SDB measures and neurobehavioral outcomes suggests the need for better measures or improved understanding of underlying causal mechanisms.

Motor memory consolidation in sleep shapes more effective neuronal representations

Learning a motor skill involves a latent process of consolidation that develops after training to enhance the skill in the absence of any practice and crucially depends on sleep. Here, we show that this latent consolidation during sleep changes the brain representation of the motor skill by reducing overall the neocortical contributions to the representation. Functional magnetic resonance brain imaging was performed during initial training and 48 h later, at retesting, on a sequential finger movement task with training followed by either a night of regular sleep or sleep deprivation. An additional night of sleep for all subjects served to rule out unspecific effects of sleep loss at retrieval testing. Posttraining sleep, but not sleep deprivation, led to improved motor skill performance at retrieval. This sleep-dependent improvement was linked to greatly reduced brain activation in prefrontal, premotor, and primary motor cortical areas, along with a stronger involvement of left parietal cortical regions. Our findings indicate that storing a motor skill during sleep reorganizes its brain representation toward enhanced efficacy.

Alteration of sleep microstructure in psychiatric disorders

Macrostructure describes the temporal organization of sleep based on successive epochs of conventional length, while microstructure, which is analyzed on the basis of the scoring of phasic events, provides additional important dynamic characteristics in the evaluation of both normal and pathological sleep processes. Relationships between sleep, sleep disorders, and psychiatric disorders are quite complex, and it clearly appears that both the macrostructure and the microstructure of sleep are valuable physiologically and clinically. Psychiatric patients often complain about their sleep, and they may show sleep abnormalities that increase with the severity of their illness. Changes in the occurrence and frequency of phasic events during sleep may be associated with specific psychiatric disorders, and may provide valuable information for both diagnosis and prognosis of these disorders.

First night effect for polysomnographic data in children and adolescents with suspected sleep disordered breathing

AIMS

To assess the presence of a first night effect (FNE) in children and adolescents and to examine if a single night polysomnography (PSG) is sufficient for diagnosing obstructive sleep apnoea syndrome (OSAS).

METHODS

Prospective case study of 70 patients (group 1: 2-6 years, n = 22; group 2: 7-12 years, n = 32; group 3: 13-17 years, n = 16) referred for OSAS. Diagnostic criteria for OSAS: one or more of the following: (1) obstructive apnoea index (OAI) > or =1; (2) obstructive apnoea hypopnoea index (oAHI) > or =2; (3) SaO2 < or =89% in association with obstruction.

RESULTS

In all age groups, but mainly in the oldest children, REMS increased during the second night, mainly at the expense of stage 2 sleep. The first night PSG correctly identified OSAS in 86%, 91%, and 100% of the children for groups 1, 2, and 3 respectively. This represents 9% false negatives for OSAS when only the first night PSG was used. All cases missed had mild OSAS, except for one with oAHI >5 on night 2. There were also seven patients with OSAS on night 1 but with a normal PSG on night 2: all had oAHI <5.

CONCLUSION

There is a FNE in children and adolescents. A single night PSG is sufficient for diagnosing OSAS, but in cases with a suggestive history and examination and with a negative first night, a second night study might be advisable.

Reduced sleep efficiency in cervical spinal cord injury; association with abolished night time melatonin secretion

STUDY DESIGN

Case-controlled preliminary observational study.

OBJECTIVE

Melatonin is usually secreted only at night and may influence sleep. We previously found that complete cervical spinal cord injury (SCI) interrupts the neural pathway required for melatonin secretion. Thus, we investigated whether the absence of night time melatonin in cervical SCI leads to sleep disturbances.

SETTING

General Clinical Research Center, Brigham and Women's Hospital, Boston, USA.

METHODS

In an ancillary analysis of data collected in a prior study, we assessed the sleep patterns of three subjects with cervical SCI plus absence of nocturnal melatonin (SCI levels: C4A, C6A, C6/7A) and two control patients with thoracic SCI plus normal melatonin rhythms (SCI levels: T4A, T5A). We also compared those results to the sleep patterns of 10 healthy control subjects.

RESULTS

The subjects with cervical SCI had significantly lower sleep efficiency (median 83%) than the control subjects with thoracic SCI (93%). The sleep efficiency of subjects with thoracic SCI was not different from that of healthy control subjects (94%). There was no difference in the proportion of the different sleep stages, although there was a significantly increased REM-onset latency in subjects with cervical SCI (220 min) as compared to subjects with thoracic SCI (34 min). The diminished sleep in cervical SCI was not associated with sleep apnea or medication use.

CONCLUSION

We found that cervical SCI is associated with decreased sleep quality. A larger study is required to confirm these findings. If confirmed, the absence of night time melatonin in cervical SCI may help explain their sleep disturbances, raising the possibility that melatonin replacement therapy could help normalize sleep in this group.

Declarative memory consolidation in humans: a prospective functional magnetic resonance imaging study

Retrieval of recently acquired declarative memories depends on the hippocampus, but with time, retrieval is increasingly sustainable by neocortical representations alone. This process has been conceptualized as system-level consolidation. Using functional magnetic resonance imaging, we assessed over the course of three months how consolidation affects the neural correlates of memory retrieval. The duration of slow-wave sleep during a nap/rest period after the initial study session and before the first scan session on day 1 correlated positively with recognition memory performance for items studied before the nap and negatively with hippocampal activity associated with correct confident recognition. Over the course of the entire study, hippocampal activity for correct confident recognition continued to decrease, whereas activity in a ventral medial prefrontal region increased. These findings, together with data obtained in rodents, may prompt a revision of classical consolidation theory, incorporating a transfer of putative linking nodes from hippocampal to prelimbic prefrontal areas.

Non-rapid eye movement sleep with low muscle tone as a marker of rapid eye movement sleep regulation

BACKGROUND

It was recently reported that epochs of non-REM sleep (NREMS) with low muscle tone represent a partial correlate of REM sleep (REMS). To further investigate this phenomenon, episodes of restricted night-time sleep (23:00-03.00 h) and subsequent morning sleep (10:00-13:00 h) were analysed.

RESULTS

Epochs of NREMS with low muscle tone (NLMT) were identified. Their frequency was higher in morning sleep than in night sleep. At night, the latency to the first occurrence of NLMT showed a bimodal distribution with modes at sleep onset and close to REMS onset. In morning sleep, the distribution was unimodal with the mode at sleep onset. An episode of NLMT at sleep onset occurred in 35.5% of the night sleep episodes and in 60.9% of the morning sleep episodes without sleep onset REMS (SOREMS). Also SOREMS occurred predominantly in morning sleep. REMS episodes were longer and NREMS episodes shorter in morning sleep than in night sleep, whereas cycle duration did not differ. Simulating the time course of slow-wave activity revealed a close correspondence between empirical and computed values for night sleep, and some discrepancies for morning sleep.

CONCLUSION

The results provide further evidence that NREMS with low muscle tone is a marker of REMS regulation. NLMT at sleep onset may represent an early manifestation of REMS.

Expanded motor and psychiatric phenotype in autosomal dominant Segawa syndrome due to GTP cyclohydrolase deficiency

BACKGROUND

Segawa syndrome due to GTP cyclohydrolase deficiency is an autosomal dominant disorder with variable expression, that is clinically characterised by l-dopa responsive, diurnally fluctuating dystonia and parkinsonian symptoms.

OBJECTIVE

To delineate the neurological and psychiatric phenotype in all affected individuals of three extended families.

METHODS

GTP cyclohydrolase deficiency was documented by biochemical analyses, enzymatic measurements in fibroblasts, and molecular investigations. All affected individuals were examined neurologically, and psychiatric data were systematically reviewed.

RESULTS

Eighteen affected patients from three families with proven GTP cyclohydrolase deficiency were identified. Eight patients presenting at less than 20 years of age had typical motor symptoms of dystonia with diurnal variation. Five family members had late-presenting mild dopa-responsive symptoms of rigidity, frequent falls, and tendonitis. Among mutation carriers older than 20 years of age, major depressive disorder, often recurrent, and obsessive-compulsive disorder were strikingly more frequent than observed in the general population. Patients responded well to medication increasing serotonergic neurotransmission and to l-dopa substitution. Sleep disorders including difficulty in sleep onset and maintenance, excessive sleepiness, and frequent disturbing nightmares were present in 55% of patients.

CONCLUSION

Physicians should be aware of this expanded phenotype in affected members of families with GTP cyclohydrolase deficiency.

Association of sleep-disordered breathing and the occurrence of stroke

RATIONALE

Sleep-disordered breathing has been linked to stroke in previous studies. However, these studies either used surrogate markers of sleep-disordered breathing or could not, due to cross-sectional design, address the temporal relationship between sleep-disordered breathing and stroke.

OBJECTIVES

To determine whether sleep-disordered breathing increases the risk for stroke.

METHODS

We performed cross-sectional and longitudinal analyses on 1,475 and 1,189 subjects, respectively, from the general population. Sleep-disordered breathing was defined by the apnea-hypopnea index (frequency of apneas and hypopneas per hour of sleep) obtained by attended polysomnography. The protocol, including polysomnography, risk factors for stroke, and a history of physician-diagnosed stroke, was repeated at 4-yr intervals.

MEASUREMENTS AND MAIN RESULTS

In the cross-sectional analysis, subjects with an apnea-hypopnea index of 20 or greater had increased odds for stroke (odds ratio, 4.33; 95% confidence interval, 1.32-14.24; p = 0.02) compared with those without sleep-disordered breathing (apnea-hypopnea index, <5) after adjustment for known confounding factors. In the prospective analysis, sleep-disordered breathing with an apnea-hypopnea index of 20 or greater was associated with an increased risk of suffering a first-ever stroke over the next 4 yr (unadjusted odds ratio, 4.31; 95% confidence interval, 1.31-14.15; p = 0.02). However, after adjustment for age, sex, and body mass index, the odds ratio was still elevated, but was no longer significant (3.08; 95% confidence interval, 0.74-12.81; p = 0.12).

CONCLUSIONS

These data demonstrate a strong association between moderate to severe sleep-disordered breathing and prevalent stroke, independent of confounding factors. They also provide the first prospective evidence that sleep-disordered breathing precedes stroke and may contribute to the development of stroke.

The sleep cycle modelled as a cortical phase transition

We present a mean-field model of the cortex that attempts to describe the gross changes in brain electrical activity for the cycles of natural sleep. We incorporate within the model two major sleep modulatory effects: slow changes in both synaptic efficiency and in neuron resting voltage caused by the ∼90-min cycling in acetylcholine, together with even slower changes in resting voltage caused by gradual elimination during sleep of somnogens (fatigue agents) such as adenosine. We argue that the change from slow-wave sleep (SWS) to rapid-eye-movement (REM) sleep can be understood as a first-order phase transition from a low-firing, coherent state to a high-firing, desychronized cortical state. We show that the model predictions for changes in EEG power, spectral distribution, and correlation time at the SWS-to-REM transition are consistent not only with those observed in clinical recordings of a sleeping human subject, but also with the on-cortex EEG patterns recently reported by Destexhe et al. [J. Neurosci.19(11), (1999) 4595-4608] for the sleeping cat.

Ventricular arrhythmia, Cheyne-Stokes respiration, and death: observations from patients with defibrillators

OBJECTIVE

To determine whether ventricular arrhythmia related to nocturnal hypoxaemia during Cheyne-Stokes respiration (CSR) explains the observation that CSR is an independent marker of death in heart failure.

DESIGN

Prospective, observational study.

PATIENTS

101 patients at high risk of clinical serious ventricular arrhythmia fitted with an implantable cardioverter-defibrillator (ICD).

MEASUREMENTS

Patients were studied at baseline for CSR during sleep. Arrhythmia requiring device discharge was used as a surrogate marker for possible sudden cardiac death.

RESULTS

101 patients (42 with CSR) were followed up for a total of 620 months. Twenty six patients experienced 432 ICD discharge episodes. Twenty four (6%), 210 (49%), 125 (29%), and 73 (17%) episodes occurred across the time quartiles 0000-0559, 0600-1159, 1200-1759, and 1800-2359, respectively. Kaplan-Meier analysis showed a relative risk of 1 (95% confidence interval 0.5 to 2.2, p = 1) for device discharge in the CSR group. The average (SED) numbers of nocturnal ICD discharges per patient per month of follow up were 0.01 (0.01) and 0.04 (0.02) for patients with and without CSR, respectively (p = 0.6).

CONCLUSION

These findings refute the proposition that CSR is related to heart failure death through nocturnal serious ventricular arrhythmia.

Respiratory control stability and upper airway collapsibility in men and women with obstructive sleep apnea

Obstructive sleep apnea (OSA) is two to three times more common in men as in women. The mechanisms leading to this difference are currently unclear but could include gender differences in respiratory stability [loop gain (LG)] or upper airway collapsibility [pharyngeal critical closing pressure (Pcrit)]. The aim of this study was to compare LG and Pcrit between men and women with OSA to determine whether the factors contributing to apnea are similar between genders. The first group of 11 men and 11 women were matched for OSA severity (mean +/- SE apnea-hypopnea index = 43.8 +/- 6.1 and 44.1 +/- 6.6 events/h). The second group of 12 men and 12 women were matched for body mass index (BMI; 31.6 +/- 1.9 and 31.3 +/- 1.8 kg/m2, respectively). All measurements were made during stable supine non-rapid eye movement sleep. LG was determined using a proportional assist ventilator. Pcrit was measured by progressively dropping the continuous positive airway pressure level for three to five breaths until airway collapse. Apnea-hypopnea index-matched women had a higher BMI than men (38.0 +/- 2.4 vs. 30.0 +/- 1.9 kg/m2; P = 0.03), but LG and Pcrit were similar between men and women (LG: 0.37 +/- 0.02 and 0.37 +/- 0.02, respectively, P = 0.92; Pcrit: 0.35 +/- 0.62 and -0.18 +/- 0.87, respectively, P = 0.63). In the BMI-matched subgroup, women had less severe OSA during non-rapid eye movement sleep (30.9 +/- 7.4 vs. 52.5 +/- 8.1 events/h; P = 0.04) and lower Pcrit (-2.01 +/- 0.62 vs. 1.16 +/- 0.83 cmH2O; P = 0.005). However, LG was not significantly different between genders (0.38 +/- 0.02 vs. 0.33 +/- 0.03; P = 0.14). These results suggest that women may be protected from developing OSA by having a less collapsible upper airway for any given degree of obesity.

Interindividual variation in sleep duration and its association with sleep debt in young adults

STUDY OBJECTIVE

To determine whether variation in sleep duration reflects variation in sleep need or self-imposed sleep restriction.

DESIGN

After habitual bedrest duration of participants was assessed during a 2-week outpatient protocol, volunteers were scheduled to sleep according to this schedule for 1 week prior to and the first night after admission to a general clinical research center. The inpatient protocol included multiple sleep latency testing on the second day and sleep recordings during a bedrest extension protocol that included 16 hours of sleep opportunity (12 hours at night and 4 hours at midday) for 3 consecutive days.

SETTING

Outpatient monitoring followed by inpatient assessment of sleep.

PARTICIPANTS

Seventeen healthy volunteers (10 women) aged 18-32 years without clinical sleep disorders.

INTERVENTIONS

Extension of sleep opportunity.

MEASUREMENTS AND RESULTS

The habitual bedrest duration varied from 6.1 to 10.3 hours. Individuals with shorter habitual bedrest duration fell asleep more quickly and frequently during the multiple sleep latency test than did those with longer habitual bedrest duration. On the first day of extended sleep opportunity, the total sleep time of all individuals was greater than their habitual bedrest duration; the average increase in total sleep time was 4.9 hours (P = 0.001). The increase in total sleep time declined across the 3 day bedrest-extension protocol (P = 0.003 for trend). During the third day of increased sleep opportunity, the total sleep time was negatively associated with habitual bedrest duration (P = 0.005); individuals with shorter habitual bedrest duration continued to sleep more than those with longer habitual bedrest duration.

CONCLUSION

Those individuals with shorter habitual sleep durations carry a higher sleep debt than do those with longer habitual sleep duration. Interindividual variation in sleep duration may primarily reflect variation in self-selected sleep restriction or wake extension.

Cerebral blood flow changes associated with fluctuations in alpha and theta rhythm during sleep onset in humans

Cerebral blood flow (CBF) is typically reduced during stable non-rapid eye movement (non-REM) sleep compared with the waking level. It is not known when in the sleep cycle these changes occur. However, spontaneous fluctuations in alpha and theta rhythm during sleep onset are associated with marked changes in cardio-respiratory control. The aim of this study was to test the hypothesis that changes in CBF would occur during sleep onset and would be related to changes in cortical activity. Middle cerebral artery velocity (MCAV) was measured using transcranial Doppler ultrasound, as an index of CBF, in 10 healthy subjects. Sleep state, ventilation, end tidal carbon dioxide (PET,CO2), arterial oxygen saturation (SaO2), mean arterial blood pressure (MABP) and cardiac R-R interval (RR) were monitored simultaneously. Immediately following the transition from alpha to theta rhythm (the transition from wake to sleep), ventilation decreased by 13.4% and tidal volume (VT) by 12.2% (P<0.01); PET,CO2 increased by 1.9% (P<0.01); respiratory frequency (fR) and SaO2 did not change significantly. MCAV increased by 9.7% (P<0.01); MABP decreased by 3.2% (P<0.01) but RR did not change significantly. Immediately following the transition from theta to alpha rhythm (spontaneous awakening), increased by 13.3% (P<0.01); VT increased by 11.4% (P<0.01); PET,CO2 decreased by 1.9% (P<0.01); MCAV decreased by 11.1% (P<0.01) and MABP decreased by 7.5%; fR, SaO2 and RR did not change significantly. These changes in MCAV during sleep onset cannot be attributed to changes in ventilation or MABP. We speculate that the changes in cerebral vascular tone during sleep onset are mediated neurally, by regulatory mechanisms linked to the changes in cortical state, and that these mechanisms are different from those regulating the longer-term reduction in CBF associated with stable non-REM sleep.

Effect of laser-assisted uvulopalatoplasty on oral airway resistance during wakefulness in obstructive sleep apnea syndrome

The aim of the study was to evaluate the effects of successful laser-assisted uvulopalatoplasty (LAUP) on oral airway resistance (R(OA)) during wakefulness in patients with OSAS. Fifteen healthy subjects (group I) and 25 subjects (group II) with moderately severe or severe obstructive sleep apnea syndrome (OSAS) proven by an overnight sleep study and who desired LAUP were enrolled. All underwent an overnight sleep study, pulmonary function testing and measurement of oral airway resistance [R(OA) (including impedance (Zrs), resistance (R) and reactance (X)] measurement by Impulse Oscillometry (IOS) (MasterScreen IOS, VIASYS Healthcare GmbH, Germany) in the upright (seated) position and then in the supine position while awake. Group II subjects had these measurements twice, both before and 3 months after LAUP. Based on the assessment of their sleep study after LAUP, they were divided into two groups: responders (group IIa) and nonresponders (group IIb). Zrs was normal in the sitting position both before and after LAUP in both groups IIa and IIb and comparable to that of group I controls. There was an increase in Zrs in the supine position in both groups IIa and IIb subjects before LAUP. After LAUP, the Zrs in group IIb subjects remained elevated, while that in group IIa subjects returned to levels comparable to those in the normal controls. OSAS patients before LAUP have abnormal R(OA) in the supine position as reflected by a high Zrs. The Zrs is improved after LAUP that successfully ameliorates OSAS.

Circadian phase-shifting effects of a laboratory environment: a clinical trial with bright and dim light

BACKGROUND

Our aims were to examine the influence of different bright light schedules on mood, sleep, and circadian organization in older adults (n = 60, ages 60-79 years) with insomnia and/or depression, contrasting with responses of young, healthy controls (n = 30, ages 20-40 years).

METHODS

Volunteers were assessed for one week in their home environments. Urine was collected over two 24-hour periods to establish baseline acrophase of 6-sulphatoxymelatonin (aMT6s) excretion. Immediately following home recording, volunteers spent five nights and four days in the laboratory. Sleep periods were fixed at eight hours in darkness, consistent with the volunteers' usual sleep periods. Volunteers were randomly assigned to one of three light treatments (four hours per day) within the wake period: (A) two hours of 3,000 lux at 1-3 hours and 13-15 hours after arising; (B) four hours of 3,000 lux at 6-10 hours after arising; (C) four hours of dim placebo light at 6-10 hours after arising. Lighting was 50 lux during the remainder of wakefulness. The resulting aMT6s acrophase was determined during the final 30 hours in the laboratory.

RESULTS

Neither mood nor total melatonin excretion differed significantly by treatment. For the three light treatments, significant and similar phase-response plots were found, indicating that the shift in aMT6s acrophase was dependent upon the circadian time of treatment. The changes in circadian timing were not significantly correlated to changes in sleep or mood.

CONCLUSION

The trial failed to demonstrate photoperiodic effects. The results suggest that even low levels of illumination and/or fixed timing of behavior had significant phase-shifting effects.

Extraocular muscle activity, rapid eye movements and the development of active and quiet sleep

Rapid eye movements (REMs), traditionally measured using the electrooculogram (EOG), help to characterize active sleep in adults. In early infancy, however, they are not clearly expressed. Here we measured extraocular muscle activity in infant rats at 3 days of age (P3), P8 and P14-15 in order to assess the ontogeny of REMs and their relationship with other forms of sleep-related phasic activity. We found that the causal relationship between extraocular muscle twitches and REMs strengthened during the first two postnatal weeks, reflecting increased control of the extraocular muscles over eye movements. As early as P3, however, phasic bursts of extraocular muscle twitching occurred in synchrony with twitching in other muscle groups, producing waves of phasic activity interspersed with brief periods of quiescence. Surprisingly, the tone of the extraocular muscles, invisible to standard EOG measures, fluctuated in synchrony with the tone of other muscle groups; focal electrical stimulation within the dorsolateral pontine tegmentum, an area that has been shown to contain wake-on neurons in P8 rats, resulted in the simultaneous activation of high tone in both nuchal and extraocular muscles. Finally, when state-dependent neocortical electroencephalographic activity was observed at P14, it had already integrated fully with sleep and wakefulness as defined using electromyographic criteria alone; this finding is not consistent with the notion that active sleep in infants at this age is 'half-activated.' All together, these results indicate exquisite temporal organization of sleep soon after birth and highlight the possible functional implications of homologous activational states in striated muscle and neocortex.

Heart rate variability in non-apneic snorers and controls before and after continuous positive airway pressure

BACKGROUND

We hypothesized that sympathetic nervous system activity (SNSA) is increased and parasympathetic nervous system activity (PNSA) is decreased during non-rapid eye movement (NREM) sleep in non-apneic, otherwise healthy, snoring individuals compared to control. Moreover, we hypothesized that these alterations in snoring individuals would be more evident during non-snoring than snoring when compared to control.

METHODS

To test these hypotheses, heart rate variability was used to measure PNSA and SNSA in 11 normotensive non-apneic snorers and 12 control subjects before and 7-days after adapting to nasal continuous positive airway pressure (nCPAP).

RESULTS

Our results showed that SNSA was increased and PNSA was decreased in non-apneic snorers during NREM compared to control. However, these changes were only evident during the study in which snoring was eliminated with nCPAP. Conversely, during periods of snoring SNSA and PNSA were similar to measures obtained from the control group. Additionally, within the control group, SNSA and PNSA did not vary before and after nCPAP application.

CONCLUSION

Our findings suggest that long-lasting alterations in autonomic function may exist in snoring subjects that are otherwise healthy. Moreover, we speculate that because of competing inputs (i.e. inhibitory versus excitatory inputs) to the autonomic nervous system during snoring, the full impact of snoring on autonomic function is most evident during non-snoring periods.

REM sleep latency and neurocognitive dysfunction in schizophrenia

BACKGROUND

Cognitive deficits-the hallmark of schizophrenic deterioration-still remain elusive as far as their pathophysiology is concerned. Various neurotransmitter systems have been implicated to explain these deficits. Abnormalities in cholinergic neurotransmission in the brain are one of the postulations; acetylcholine has also been postulated to regulate rapid eye movement (REM) sleep, especially REM latency. Thus, REM latency in patients with schizophrenia might provide a non-invasive window to look into the cholinergic functions of the brain.

AIM

To study REM sleep measures and neurocognitive function in schizophrenia, and the changes occurring in these parameters following pharmacological treatment.

METHODS

Thirty subjects (15 with schizophrenia and 15 normal non-relative controls) were evaluated in this study. Most patients with schizophrenia had prominent negative symptoms and deficits in the performance in neurocognitive tests battery. They were treated with antipsychotics for a variable period of time and post-treatment evaluation was done using the same battery of neurocognitive tests and polysomnography. Patients were either drug-naïve or kept drug-free for at least two weeks both at baseline as well as at the post-treatment stage.

RESULTS

A positive correlation between the severity of negative symptoms and neurocognitive deficits (especially on the Wisconsin Card Sorting), and a negative correlation between these two parameters and REM latency was observed.

CONCLUSION

It can be hypothesized that the acetylcholine deficit model of dementia cannot be applied to schizophrenic dementia, rather a hypercholinergic state results. This state warrants anticholinergic medication as a treatment option for negative symptoms of schizophrenia.

An E-health solution for automatic sleep classification according to Rechtschaffen and Kales: validation study of the Somnolyzer 24 x 7 utilizing the Siesta database

To date, the only standard for the classification of sleep-EEG recordings that has found worldwide acceptance are the rules published in 1968 by Rechtschaffen and Kales. Even though several attempts have been made to automate the classification process, so far no method has been published that has proven its validity in a study including a sufficiently large number of controls and patients of all adult age ranges. The present paper describes the development and optimization of an automatic classification system that is based on one central EEG channel, two EOG channels and one chin EMG channel. It adheres to the decision rules for visual scoring as closely as possible and includes a structured quality control procedure by a human expert. The final system (Somnolyzer 24 x 7) consists of a raw data quality check, a feature extraction algorithm (density and intensity of sleep/wake-related patterns such as sleep spindles, delta waves, SEMs and REMs), a feature matrix plausibility check, a classifier designed as an expert system, a rule-based smoothing procedure for the start and the end of stages REM, and finally a statistical comparison to age- and sex-matched normal healthy controls (Siesta Spot Report). The expert system considers different prior probabilities of stage changes depending on the preceding sleep stage, the occurrence of a movement arousal and the position of the epoch within the NREM/REM sleep cycles. Moreover, results obtained with and without using the chin EMG signal are combined. The Siesta polysomnographic database (590 recordings in both normal healthy subjects aged 20-95 years and patients suffering from organic or nonorganic sleep disorders) was split into two halves, which were randomly assigned to a training and a validation set, respectively. The final validation revealed an overall epoch-by-epoch agreement of 80% (Cohen's kappa: 0.72) between the Somnolyzer 24 x 7 and the human expert scoring, as compared with an inter-rater reliability of 77% (Cohen's kappa: 0.68) between two human experts scoring the same dataset. Two Somnolyzer 24 x 7 analyses (including a structured quality control by two human experts) revealed an inter-rater reliability close to 1 (Cohen's kappa: 0.991), which confirmed that the variability induced by the quality control procedure, whereby approximately 1% of the epochs (in 9.5% of the recordings) are changed, can definitely be neglected. Thus, the validation study proved the high reliability and validity of the Somnolyzer 24 x 7 and demonstrated its applicability in clinical routine and sleep studies.

Sleep quality deteriorates over a binge--abstinence cycle in chronic smoked cocaine users

RATIONALE

In cocaine dependent individuals, changes in subjective and objective sleep quality accompany their characteristic binge-abstinence cycle. Preliminary studies suggest that sleep quality may decline with prolonged abstinence. Reported here are results of the most extensive study to date on sleep abnormalities during cocaine binge and confirmed abstinence under controlled conditions.

OBJECTIVES

The purpose of the current study was to use an experimental, inpatient model of the cocaine binge and abstinence cycle to examine the course and magnitude of sleep disturbances during cocaine use and abstinence.

METHODS

Five inpatient non-treatment seeking cocaine users completed 3 baseline days of drug abstinence followed by 3 days of medically monitored "binge" cocaine use, and then 15 days of drug abstinence. Physiological sleep was recorded with polysomnography and the Nightcap ambulatory monitor, while subjective sleep was assessed by questionnaire.

RESULTS

Across 3 days of binge cocaine use and 15 subsequent days of confirmed drug abstinence, mean sleep duration, efficiency and latency changed in the direction of poorer sleep quality. In contrast, subjective reports of sleep quality remained unchanged across the same period.

CONCLUSIONS

Physiological sleep quality deteriorated from days when cocaine was used across the first 2 weeks of confirmed drug abstinence. In contrast, subjective reports of sleep quality remained unchanged across the same period. We postulate that this dissociation between objective and subjective sleep quality results from a cocaine-use related disruption of the sleep homeostat. Worsening sleep quality during cocaine abstinence may contribute to the risk of relapse and its treatment may offer novel therapeutic strategies for cocaine dependence.

Inhibitory and excitatory intracortical circuits across the human sleep-wake cycle using paired-pulse transcranial magnetic stimulation

Studies using single-pulse transcranial magnetic stimulation (TMS) have shown that excitability of the corticospinal system is systematically reduced in natural human sleep as compared to wakefulness with significant differences between sleep stages. However, the underlying excitatory and inhibitory interactions on the corticospinal system across the sleep-wake cycle are poorly understood. Here, we specifically asked whether in the motor cortex short intracortical inhibition (SICI) and facilitation (ICF) can be elicited at all in sleep using the paired-pulse TMS protocol, and if so, how SICI and ICF vary across sleep stages. We studied 28 healthy subjects at interstimulus intervals of 3 ms (SICI) and 10 ms (ICF), respectively. Magnetic stimulation was performed over the hand area of the motor cortex using a focal coil and evoked motor potentials were recorded from the contralateral first dorsal interosseus muscle (1DI). Relevant data was obtained from 13 subjects (NREM 2: n=7; NREM 3/4: n=7; REM: n=7). Results show that both SICI and ICF were present in NREM sleep. SICI was significantly enhanced in NREM 3/4 as compared to wakefulness and all other sleep stages whereas in NREM 2 neither SICI nor ICF differed from wakefulness. In REM sleep SICI was in the same range as in wakefulness, but ICF was entirely absent. These results in humans support the hypothesis derived from animal experiments which suggests that intracortical inhibitory mechanisms are involved in the control of neocortical pyramidal cells in NREM and REM sleep, but along different intraneuronal circuits. Further, our findings suggest that cortical mechanisms may additionally contribute to the inhibition of spinal motoneurones in REM sleep.

Sleep EEG evidence of sex differences in adolescent brain maturation

STUDY OBJECTIVES

The steep decline in slow-wave (delta) electroencephalogram (EEG) intensity across adolescence is a prominent feature of late brain maturation. As a first step in determining whether the adolescent delta decline is similar in both sexes, we compared cross-sectional sleep EEG data from 9- and 12-year-old boys and girls.

DESIGN

All-night EEG recordings, 6 months apart, were conducted on each subject.

SETTING

EEG was recorded in the subjects' homes.

PARTICIPANTS

Thirty-two 9-year-olds and 38 12-year-olds are enrolled in a 4-year longitudinal study of adolescent sleep. There are equal numbers of each sex in both age cohorts.

INTERVENTIONS

N/A.

MEASUREMENTS

Using ambulatory recorders, EEG was recorded in the subjects' homes on their normal sleep schedule. For each of the 2 semi-annual recording periods, data from the 10 subjects from each age-sex group with the cleanest (fewest artifacts) signals were selected for crosssectional comparisons of visual scoring and EEG variables. All artifact-free 20-second non-rapid eye movement epochs were analyzed with power spectral and period-amplitude analysis.

RESULTS

In the 12-year-old cohort, delta power per minute was 37% higher in boys than girls. The 9-year-old cohort showed no sex difference. A second recording 6 months later produced similar results.

CONCLUSION

These cross-sectional data indicate that girls begin the steep adolescent decline in slow-wave EEG earlier than boys. We hypothesize that this reflects an earlier onset of adolescent synaptic pruning in females.

Medroxyprogesterone improves nocturnal breathing in postmenopausal women with chronic obstructive pulmonary disease

BACKGROUND

Progestins as respiratory stimulants in chronic obstructive pulmonary disease (COPD) have been investigated in males and during wakefulness. However, sleep and gender may influence therapeutic responses. We investigated the effects of a 2-week medroxyprogesterone acetate (MPA) therapy on sleep and nocturnal breathing in postmenopausal women.

METHODS

A single-blind placebo-controlled trial was performed in 15 postmenopausal women with moderate to severe COPD. A 12-week trial included 2-week treatment periods with placebo and MPA (60 mg/d/14 days). All patients underwent a polysomnography with monitoring of SaO2 and transcutaneous PCO2 (tcCO2) at baseline, with placebo, with medroxyprogesterone acetate (MPA 60 mg/d/14 days), and three and six weeks after cessation of MPA.

RESULTS

Thirteen patients completed the trial. At baseline, the average +/- SD of SaO2 mean was 90.6 +/- 3.2 % and the median of SaO2 nadir 84.8 % (interquartile range, IQR 6.1). MPA improved them by 1.7 +/- 1.6 %-units (95 % confidence interval (CI) 0.56, 2.8) and by 3.9 %-units (IQR 4.9; 95% CI 0.24, 10.2), respectively. The average of tcCO2 median was 6.0 +/- 0.9 kPa and decreased with MPA by 0.9 +/- 0.5 kPa (95% CI -1.3, -0.54). MPA improved SaO2 nadir and tcCO2 median also during REM sleep. Three weeks after cessation of MPA, the SaO2 mean remained 1.4 +/- 1.8 %-units higher than at baseline, the difference being not significant (95% CI -0.03, 2.8). SaO2 nadir was 2.7 %-units (IQR 4.9; 95% CI 0.06, 18.7) higher than at baseline. Increases in SaO2 mean and SaO2 nadir during sleep with MPA were inversely associated with baseline SaO2 mean (r = -0.70, p = 0.032) and baseline SaO2 nadir (r = -0.77, p = 0.008), respectively. Treatment response in SaO2 mean, SaO2 nadir and tcCO2 levels did not associate with pack-years smoked, age, BMI, spirometric results or sleep variables.

CONCLUSION

MPA-induced respiratory improvement in postmenopausal women seems to be consistent and prolonged. The improvement was greater in patients with lower baseline SaO2 values. Long-term studies in females are warranted.

Identifying target regions for vigilance improvement under hormone replacement therapy in postmenopausal syndrome patients by means of electroencephalographic tomography (LORETA)

RATIONALE

Daytime fatigue, which at the neurophysiological level is due to vigilance decrements, is a frequent complaint in postmenopausal women.

OBJECTIVES

In a three-arm, 2-month, parallel group-design study, vigilance-promoting effects of a novel continuous combination (=Climodien 2/3) of estradiol valerate (EV; 2 mg) and dienogest (DNG; 3 mg) were compared with the effects of both EV alone and placebo in 55 insomniac, postmenopausal syndrome patients.

METHODS

Low-resolution brain electromagnetic tomography (LORETA) was undertaken to identify the cerebral target regions of hormone replacement therapy.

RESULTS

An omnibus significance test revealed Climodien to increase activity in 882 of 2,394 voxels in the alpha-2 band, followed by 733, 706, and 664 voxels in the beta-2, beta-1, and beta-3 bands, and 509 voxels in the delta band, whereas 2 mg EV alone did not produce a significant suprathreshold activity. Current density increased predominantly in the right hemisphere, which had already been described in the literature as the center of the vigilance system. In the fast alpha range, which plays a major role in the context of vigilance, increased activity was found in the right prefrontal, temporal, and superior parietal cortices, i.e., those brain areas of the right-sided fronto-parietal neuronal network that are responsible for sustained attention. A further activity increase was seen in the anterior cingulate gyrus associated with attentional control and conflict monitoring. The right temporal lobe showed increased current density in all frequency bands.

CONCLUSIONS

Electroencephalographic tomography (LORETA) identified the right-hemispheric vigilance system as the target region of Climodien.

The normal-weight snorer: polysomnographic study and correlation with upper airway morphological alterations

Obesity is recognized as playing an important role in causing snoring and in turning simple snoring into obstructive sleep apnea syndrome (OSAS). From our series of patients with sleep disturbances, we studied a group of 43 normal-weight snorers in whom we detected a significant number of OSAS episodes. An articulated diagnostic protocol was adopted, and Müller's maneuver was extensively applied. The resulting data were compared to data from a group of 43 obese patients from the same series. The major risk factor for developing OSAS in normal-weight snorers appears to be anatomic abnormalities, in particular, septal deviation and base of tongue hypertrophy. Soft palate hypertrophy alone is not enough, although in obese snorers it can produce a sleep disorder. The normal-weight snorer needs to be thoroughly investigated because of the significant risk of developing OSAS and for the detection of multiple concomitant sites of obstruction.

The ontogeny of mammalian sleep: a response to Frank and Heller (2003)

In a recent review, Frank and Heller (2003) provided support for their 'presleep theory' of sleep development. According to this theory, rapid eye movement (REM) and non-rapid eye movement (Non-REM) sleep in rats emerge from a common 'dissociated' state only when the neocortical EEG differentiates at 12 days of age (P12). Among the assumptions and inferences associated with this theory is that sleep before EEG differentiation is only 'sleep-like' and can only be characterized using behavioral measures; that the neural mechanisms governing presleep are distinct from those governing REM and Non-REM sleep; and that the presleep theory is the only theory that can account for developmental periods when REM and Non-REM sleep components appear to overlap. Evidence from our laboratory and others, however, refutes or casts doubt on these and other assertions. For example, infant sleep in rats is not 'sleep-like' in that it satisfies nearly every criterion used to characterize sleep across species. In addition, beginning as early as P2 in rats, myoclonic twitching occurs only against a background of muscle atonia, indicating that infant sleep is not dissociated and that electrographic measures are available for sleep characterization. Finally, improved techniques are leading to new insights concerning the neural substrates of sleep during early infancy. Thus, while many important developmental questions remain, the presleep theory, at least in its present form, does not accurately reflect the phenomenology of infant sleep.

Obstructive sleep apnea in sleepy pediatric psychiatry clinic patients: polysomnographic and clinical correlates

STUDY OBJECTIVES

To assess the incidence of polysomnographically defined obstructive sleep apnea (OSA) in pediatric psychiatric clinic patients reporting daytime sleepiness on questionnaire, and to identify diagnostic correlates for OSA in this grouping.

DESIGN

Prospective and observational.

SETTING

Outpatient pediatric psychiatry clinic, outpatient sleep medicine clinic, AASM-accredited hospital-based sleep laboratory.

SUBJECTS

Children aged 3 to 16 years, reporting daytime sleepiness on questionnaire (N = 74); exclusions: adenotonsillectomy and trisomy 21.

INTERVENTIONS

Parents and children completed a questionnaire designed and validated for identifying pediatric patients with OSA at the pediatric psychiatry clinic. Patients with at least one positive response as to daytime sleepiness (N = 74) were referred for a history and physical by a board-certified sleep medicine physician before in-hospital polysomnography utilizing a routine apnea montage with parent or legal guardian sleeping in room.

RESULTS

Mean apnea-hypopnea index (AHI) for this pediatric psychiatry clinic grouping was 5.5. Of these patients, 39.2% had an AHI > 5.0. Mean AHI for patients with attention deficit/hyperactivity disorder (AD/HD) was 7.1; without AD/HD it was 4.5 (p < 0.05). Mean AHI for patients with tonsillar hypertrophy was 6.5 compared with 4.4 for those without tonsillar hypertrophy (p < 0.05).

CONCLUSION

In a clinical grouping of pediatric psychiatry patients reporting daytime sleepiness by questionnaire, polysomnographically defined OSA is common. Both AD/HD as diagnosed using DSM-IV criteria and tonsillar hypertrophy based on clinical exam by a sleep medicine physician are diagnostic correlates for polysomnographically defined OSA in this pediatric psychiatry clinic grouping of patients.

Self-awakening prevents acute rise in blood pressure and heart rate at the time of awakening in elderly people

Self-awakening, waking up at a designated time decided before sleeping, could prevent failure in the blood circulation vessel system such as heart attack, acute increases in heart rate or blood pressure upon waking. Previous research showed that anticipatory changes occurred in heart rate prior to awakening from a short nap by means of self-awakening for young participants. However, the effects of self-awakening remained unclear for elderly people. The present study examined the effects of self-awakening on heart rate and blood pressure in a short afternoon nap (20 min) among the elderly. Nine participants [74.1 (SD = 5.01) years old] underwent both self-awakening and forced-awakening conditions. In the self-awakening condition, it was revealed that blood pressure gradually increased before the scheduled time of awakening, and that heart rate did not show a rapid increase at arousal. In contrast, forced-awakening induced acute increases in both heart rate and blood pressure. These results suggest that self-awakening facilitates a more smooth transition from sleep to wakefulness via autonomic activation before the time of self-awakening.

Approximate entropy in the electroencephalogram during wake and sleep

Entropy measurement can discriminate among complex systems, including deterministic, stochastic and composite systems. We evaluated the changes of approximate entropy (ApEn) in signals of the electroencephalogram (EEG) during sleep. EEG signals were recorded from eight healthy volunteers during nightly sleep. We estimated the values of ApEn in EEG signals in each sleep stage. The ApEn values for EEG signals (mean +/- SD) were 0.896 +/- 0.264 during eyes-closed waking state, 0.738 +/- 0.089 during Stage I, 0.615 +/- 0.107 during Stage II, 0.487 +/- 0.101 during Stage II, 0.397 +/- 0.078 during Stage IV and 0.789 +/- 0.182 during REM sleep. The ApEn values were found to differ with statistical significance among the six different stages of consciousness (ANOVA, p<0.001). ApEn of EEG was statistically significantly lower during Stage IV and higher during wake and REM sleep. We conclude that ApEn measurement can be useful to estimate sleep stages and the complexity in brain activity.

Discrepancy in Polysomnography Scoring for a Patient with Obstructive Sleep Apnea Hypopnea Syndrome

Overnight polysomnography (PSG) is indispensable for diagnosis of obstructive sleep apnea hypopnea syndrome. However, studies on interscorer agreement on PSG scoring between laboratories are few. The purpose of this study was to examine the reliability of interscorer agreement on PSG scoring among 16 sleep laboratories in Japan. We found a relatively moderate interscorer reliability of the index of oxygen desaturation and arousal during sleep, but a relatively low reliability of the index of transient reduction in and complete cessation of breathing (apnea hypopnea index). The median rate of interscorer coincidence of sleep staging was the lowest for slow wave (deep) sleep (23.5%), followed by those for Stage 1 (59.8%), Wake (73.2%) and Stage 2 (74.2%) in this order, and rapid eye movement was the most reliably identified stage (91.3%). The median rate of interscorer coincidence for all stages was 71.8%. The present study demonstrates that scorers tend to analyze PSG data according to a relatively empirical decision as opposed to a rule-dependent decision. Further detailed scoring manuals are required to decrease the interscorer discrepancy in PSG scoring.