Showing papers in "Journal of Sleep Research in 2004"

The nature of arousal in sleep.

Abstract: The role of arousals in sleep is gaining interest among both basic researchers and clinicians. In the last 20 years increasing evidence shows that arousals are deeply involved in the pathophysiology of sleep disorders. The nature of arousals in sleep is still a matter of debate. According to the conceptual framework of the American Sleep Disorders Association criteria, arousals are a marker of sleep disruption representing a detrimental and harmful feature for sleep. In contrast, our view indicates arousals as elements weaved into the texture of sleep taking part in the regulation of the sleep process. In addition, the concept of micro-arousal (MA) has been extended, incorporating, besides the classical low-voltage fast-rhythm electroencephalographic (EEG) arousals, high-amplitude EEG bursts, be they like delta-like or K-complexes, which reflects a special kind of arousal process, mobilizing parallely antiarousal swings. In physiologic conditions, the slow and fast MA are not randomly scattered but appear structurally distributed within sleep representing state-specific arousal responses. MA preceded by slow waves occurs more frequently across the descending part of sleep cycles and in the first cycles, while the traditional fast type of arousals across the ascending slope of cycles prevails during the last third of sleep. The uniform arousal characteristics of these two types of MAs is supported by the finding that different MAs are associated with an increasing magnitude of vegetative activation ranging hierarchically from the weaker slow EEG types (coupled with mild autonomic activation) to the stronger rapid EEG types (coupled with a vigorous autonomic activation). Finally, it has been ascertained that MA are not isolated events but are basically endowed with a periodic nature expressed in non-rapid eye movement (NREM) sleep by the cyclic alternating pattern (CAP). Understanding the role of arousals and CAP and the relationship between physiologic and pathologic MA can shed light on the adaptive properties of the sleeping brain and provide insight into the pathomechanisms of sleep disturbances. Functional significance of arousal in sleep, and particularly in NREM sleep, is to ensure the reversibility of sleep, without which it would be identical to coma. Arousals may connect the sleeper with the surrounding world maintaining the selection of relevant incoming information and adapting the organism to the dangers and demands of the outer world. In this dynamic perspective, ongoing phasic events carry on the one hand arousal influences and on the other elements of information processing. The other function of arousals is tailoring the more or less stereotyped endogenously determined sleep process driven by chemical influences according to internal and external demands. In this perspective, arousals shape the individual course of night sleep as a variation of the sleep program.

Sleep quantity, sleep difficulties and their perceived consequences in a representative sample of some 2000 British adults

Abstract: Sleep problems and sleep restriction are popular topics of discussion, but few representative data are available. We document Britain's sleep based on a nationally representative sample of 1997, 16-93 year olds, who participated in face-to-face interviews. Fifty-eight per cent of respondents reported sleep problems on one or more nights the previous week and 18% reported that the sleep they obtained was insufficient on the majority of nights. Sleep durations were longest in the youngest participants (16-24 years), who slept on average 1 h longer than the 7.04 (SD 1.55) sample average. Sleep duration showed no appreciable change beyond middle age. Men and women reported sleeping similar amounts but women reported more sleep problems. Men reported sleeping less when there were more children in their household. Workers (i.e. employees) reported sleeping less on workdays than on non-workdays, but those based at home and those not employed did not. Inability to switch off from work was related to sleep duration on non-workdays. Across all participants average sleep duration exhibited a non-monotonic association with quality of life (i.e. contribution of sleep to energy, satisfaction and success in work, home and leisure activities). Quality of life was positively associated with sleep duration, for durations up to 9 h, but negatively associated with quality of life beyond this. Comparison of our data with the US national sleep poll revealed that Britain sleeps as little or less, whereas a comparison with data reported 40 years ago revealed no statistically reliable reductions. Although we may not sleep less than four decades ago, when we report sleeping less we also tend to associate that lack of sleep with poor performance and quality of life.

Sleep problems in children with autism.

Abstract: Autism is a developmental disability characterized by severe deficits in social interaction and communication, and the presence of repetitive-ritualistic behaviors. Sleep problems are frequently reported by parents of children with autism with prevalence estimates of 44-83% for sleep disorders in this population. To better understand sleep in autism, we surveyed sleep problems in 210 children with autism using a Likert-based questionnaire for parent report. The most frequently reported sleep problems included difficulty in falling asleep, restless sleep, not falling asleep in own bed, and frequent wakenings. Least frequently reported sleep problems were sleep walking, morning headaches, crying during sleep, apnea, and nightmares. When surveys were divided into mental retardation (MR)/not MR categories, no significant differences were identified in frequencies of reported sleep problems except for waking at night which occurred much more frequently in the MR group. There was also no difference in sleep problems related to age of the child other than nocturnal enuresis. An association was noted between certain medical problems and sleep problems. Vision problems, upper respiratory problems, and runny nose were associated with decreased nighttime sleep. Vision problems, poor appetite, and poor growth were associated with increased nighttime waking. Poor appetite and poor growth were associated with decreased willingness to fall asleep. This study confirms a high prevalence of sleep problems reported by parents of children with autism and points to the need for more systematic research as an initial step in developing treatment strategies.

Neurobehavioral correlates of sleep-disordered breathing in children.

Abstract: The effects of sleep-disordered breathing (SDB) on neurobehavioral function were examined in two matched groups of children from the general population. Thirty-five children with polysomnographically confirmed SDB were matched for ethnicity, age, gender, maternal educational attainment, and maternal smoking, to healthy children with no evidence of SDB. Children with SDB had significantly lower mean scores on the Differential Ability Scales for General Conceptual Ability (similar to IQ) and for the Non-verbal Cluster. On the neuropsychology assessment battery (NEPSY), children with SDB scored significantly lower than the control group on the attention/executive function domain and two subtests within that domain, one measuring visual attention and the other executive function. In addition, children with SDB scored significantly lower than the controls on one subtest from the NEPSY language domain: Phonological Processing. This subtest measures phonological awareness, a skill that is critical for learning to read. No differences in behavior, as measured by the Child Behavior Checklist (CBCL) or the Conners' Parent Rating Scale, were found between the two groups. Using a novel algorithm to assess sleep pressure, we found that children with SDB were significantly sleepier than controls. Furthermore, total arousal index was negatively correlated with neurocognitive abilities, suggesting a role for sleep fragmentation in pediatric SDB-induced cognitive dysfunction.

Comparative utility of instruments for monitoring sleepiness‐related performance decrements in the operational environment

Abstract: SUMMARY As both military and commercial operations increasingly become continuous, 24-h-per-day enterprises, the likelihood of operator errors or inefficiencies caused by sleep lossand/or circadian desynchrony also increases Avoidance of such incidents requires thetimely application of appropriate interventions – which, in turn, depend on the abilityto measure and monitor the performance capacity of individuals in the operationalenvironment Several factors determine the potential suitability of candidate measures,including their relative sensitivity, reliability, content validity, intrusiveness andcumbersomeness/fieldability In the present study, the relative sensitivity (defined asthe ratio of effect size to 95% confidence interval) of several measures to the effects ofsleep loss was compared in a sleep restriction experiment, in which groups were allowed3, 5, 7, or 9 h time in bed (TIB) across seven consecutive nights Of the measurescompared, the Psychomotor Vigilance Test was among the most sensitive to sleeprestriction, was among the most reliable with no evidence of learning over repeatedadministrations, and possesses characteristics that make it among the most practical foruse in the operational environmentkeywords effect size, fieldability, performance measures, sleep loss

The relationship of nightmare frequency and nightmare distress to well‐being

Abstract: Nightmares can be defined as very disturbing dreams, the events or emotions of which cause the dreamer to wake up. In contrast, unpleasant dreams can be defined in terms of a negative emotional rating of a dream, irrespective of whether or not the emotions or events of the dream woke the dreamer. This study addresses whether frequency of unpleasant dreams is a better index of low well-being than is frequency of nightmares. A total of 147 participants reported their nightmare frequency retrospectively and then kept a log of all dreams, including nightmares, for 2 weeks, and rated each dream for pleasantness/unpleasantness. Anxiety, depression, neuroticism, and acute stress were found to be associated with nightmare distress (ND) (the trait-like general level of distress in waking-life caused by having nightmares) and prospective frequency of unpleasant dreams, and less so with the mean emotional tone of all dreams, or retrospective or prospective nightmare frequency. Correlations between low well-being and retrospective nightmare frequency became insignificant when trait ND was controlled for, but correlations with prospective unpleasant dream frequency were maintained. The reporting of nightmares may thus be confounded and modulated by trait ND: such confounding does not occur for the reporting of unpleasant dreams in general. Thus there may be attributional components to deciding that one has been awoken by a dream, which can affect estimated nightmare frequency and its relationship with well-being. Underestimation of nightmare frequency by the retrospective questionnaire compared with logs was found to be a function of mean dream unpleasantness and ND.

Age, performance and sleep deprivation.

Abstract: Young subjects are frequently involved in sleep-related accidents. They could be more affected than older drivers by sleep loss and therefore worsen their driving skills quicker, or have a different perception of their level of impairment. To test these hypotheses we studied variations of reaction time (RT), a fundamental prerequisite for safe performing, as measured by lapses, i.e. responses > or = 500 ms and self-assessment of performance and sleepiness after a night awake and after a night asleep in a balanced crossover design in young versus older healthy subjects. Ten young (20-25 years old) and 10 older volunteers (52-63 years old) were tested with and without 24 h of sleep deprivation. Without sleep deprivation, RTs were slower in older subjects than in the younger ones. However, after sleep deprivation, the RTs of young subjects increased while that of the older subjects remained almost unaffected. Sleepiness and self-perception of performance were equally affected in both age groups showing different perception of performance in the age groups. Our findings are discussed in terms of vulnerability to sleep-related accidents.

Interrater reliability between scorers from eight European sleep laboratories in subjects with different sleep disorders.

Abstract: Interrater variability of sleep stage scorings is a well-known phenomenon. The SIESTA project offered the opportunity to analyse interrater reliability (IRR) between experienced scorers from eight European sleep laboratories within a large sample of patients with different (sleep) disorders: depression, general anxiety disorder with and without non-organic insomnia, Parkinson's disease, period limb movements in sleep and sleep apnoea. The results were based on 196 recordings from 98 patients (73 males: 52.3 +/- 12.1 years and 25 females: 49.5 +/- 11.9 years) for which two independent expert scorings from two different laboratories were available. Cohen's kappa was used to evaluate the IRR on the basis of epochs and intraclass correlation was used to analyse the agreement on quantitative sleep parameters. The overall level of agreement when five different stages were distinguished was kappa = 0.6816 (76.8%), which in terms of kappa reflects a 'substantial' agreement (Landis and Koch, 1977). For different groups of patients kappa values varied from 0.6138 (Parkinson's disease) to 0.8176 (generalized anxiety disorder). With regard to (sleep) stages, the IRR was highest for rapid eye movement (REM), followed by Wake, slow-wave sleep (SWS), non-rapid eye movement 2 (NREM2) and NREM1. The results of regression analysis showed that age and sex only had a statistically significant effect on kappa when the (sleep) stages are considered separately. For NREM2 and SWS a statistically significant decrease of IRR with age has been observed and the IRR for SWS was lower for males than for females. These variations of IRR most probably reflect changes of the sleep electroencephalography (EEG) with age and gender.

The clinical spectrum of narcolepsy with cataplexy: a reappraisal

Abstract: In the absence of a golden standard for the diagnosis of narcolepsy, the clinical spectrum of disorder remains controversial. The aims of this study were (1) to determine frequency and characteristics of sleep-wake symptoms in patients with narcolepsy with cataplexy, (2) to compare clinical characteristics with results of ancillary tests, and (3) to identify factors that discriminate narcolepsy from other conditions with excessive daytime sleepiness (EDS). We prospectively studied 57 narcoleptics with cataplexy, 56 patients with non-narcoleptic hypersomnia (H), and 40 normal controls (No). Based on suggested and published criteria, we differentiated between narcoleptics with definite cataplexy (N) and narcoleptics without definite cataplexy (possible cataplexy, NpC). Assessment consisted of questionnaires [all patients and controls, including the Ullanlinna Narcolepsy Score (UNS)], polysomnography (all patients), multiple sleep latency test (MSLT) and human leukocyte antigen typing (in most narcoleptics). A new narcolepsy score based on five questions was developed. Data were compared with those of 12 hypocretin-deficient narcoleptics (N-hd). There were significant differences between N and NpC (including mean sleep latency on MSLT), but none between N and N-hd. A score of sleep propensity during active situations (SPAS) and the frequency of sleep paralysis/hallucinations at sleep onset, dreams of flying, and history of sleep shouting discriminated N from H and No (P < 0.001). Cataplexy-like symptoms in H (18%) and No (8%) could be discriminated from 'true' cataplexy in N on the basis of topography of motor effects, triggering emotions and triggering situations (P < 0.001). Our narcolepsy score had a similar sensitivity (96% versus 98%) but a higher specificity (98% versus 56%) than the UNS. Analysis of co-occurring symptoms in narcolepsy revealed two symptom complexes: EDS, cataplexy, automatic behaviors; and sleep paralysis, hallucinations, parasomnias. Low/undetectable cerebrospinal fluid hypocretin-1 levels and a history of definite cataplexy identify similar subgroups of narcoleptics. Specific questions on severity of EDS (SPAS score) and characteristics of cataplexy allow the recognition of subgroups of narcoleptics and their differentiation from non-narcoleptic EDS patients, including those reporting cataplexy-like episodes. The existence of co-occurring symptoms supports the hypothesis of a distinct pathophysiology of single narcoleptic symptoms.

Inter- and intra-individual variability in performance near the circadian nadir during sleep deprivation.

Abstract: The study purpose was to assess inter- and intra-individual variability in neurobehavioral function near the circadian nadir during sleep deprivation and conduct exploratory factor analyses to assess relationships among alertness and performance measures during sleep deprivation. Twenty-five healthy individuals (16 females) aged 18-25 years participated. Participants were sleep deprived for two nights under controlled laboratory conditions using a modified constant routine procedure. A comprehensive battery of neurobehavioral performance tests, subjective sleepiness (SSS), and objective alertness (MWT) were assessed. Seventeen of the 22 neurobehavioral measures were impaired by sleep deprivation (all P < 0.01). The use of multiple neurobehavioral performance measures revealed impairments for all individuals during sleep deprivation. However, sleep deprivation effects were task dependent within and between individuals. Gender contributed minimally to inter-individual variability in performance. Exploratory factor analysis reduced the 22 measures to seven independent factors. Our findings indicate that no individual was especially vulnerable or resistant to the performance impairing effects of sleep deprivation. Instead, inter- and intra-individual variability in performance during sleep deprivation was task dependent. The finding that subjective sleepiness and objective alertness were not related to any performance measure during sleep deprivation suggests that these measures may assess independent brain functions.

Suppression of sleepiness and melatonin by bright light exposure during breaks in night work

Abstract: Night work is non-optimal for performance and recuperation because of a lack of circadian influence that fully promote a night orientation. Our study assessed, in an industrial setting, the effects of bright light exposure (BL) on sleepiness, sleep and melatonin, during night work and during the following readaptation to day work. In a crossover design, 18 workers at a truck production plant were exposed to either BL (2500 lx) during breaks or normal light during four consecutive weeks. Twenty minute breaks were initiated by 67% of the workers between 03:00 and 04:00 hours. Sleep/wake patterns were assessed through actigraphs and ratings were given in a sleep/wake diary. Saliva melatonin was measured at 2-h intervals before, during and after night shift weeks. A significant interaction demonstrated a reduction of sleepiness in the BL condition particularly on the first two nights at 04:00 and 06:00 hours. Day sleep in the BL condition was significantly lengthened. Bright light administration significantly suppressed melatonin levels during night work and most strongly at 02:00 hours. Daytime melatonin during the readaptation after night work remained unaffected. The present findings demonstrate the feasibility and benefits of photic stimulation in industrial settings to increase adaptation to night work.

Immediate and delayed incorporations of events into dreams: further replication and implications for dream function

Abstract: The incorporation of memories into dreams is characterized by two types of temporal effects: the day-residue effect, involving immediate incorporations of events from the preceding day, and the dream-lag effect, involving incorporations delayed by about a week. This study was designed to replicate these two effects while controlling several prior methodological problems and to provide preliminary information about potential functions of delayed event incorporations. Introductory Psychology students were asked to recall dreams at home for 1 week. Subsequently, they were instructed to select a single dream and to retrieve past events related to it that arose from one of seven randomly determined days prior to the dream (days 1-7). They then rated both their confidence in recall of events and the extent of correspondence between events and dreams. Judges evaluated qualities of the reported events using scales derived from theories about the function of delayed incorporations. Average ratings of correspondences between dreams and events were high for predream days 1 and 2, low for days 3 and 4 and high again for days 5-7, but only for participants who rated their confidence in recall of events as high and only for females. Delayed incorporations were more likely than immediate incorporations to refer to events characterized by interpersonal interactions, spatial locations, resolved problems and positive emotions. The findings are consistent with the possibility that processes with circaseptan (about 7 days) morphology underlie dream incorporation and that these processes subserve the functions of socio-emotional adaptation and memory consolidation.

Sleep complaints in patients with myotonic dystrophy.

Abstract: The aim of this study was to document the clinical picture of excessive daytime sleepiness (EDS) and of other sleep disturbances, and to study the relationship of daytime sleepiness to anthropometric data, muscular impairment, and CTG trinucleotide repeat expansion in myotonic dystrophy type 1 (DM1). A total of 157 DM1 patients were surveyed using a modified version of the Sleep Questionnaire and Assessment of Wakefulness. Other measurements included muscular impairment rating and the size of the trinucleotide repeat. Factor analysis and reliability estimates were used to produce a daytime sleepiness scale with five items of the questionnaire. Thirty-eight healthy family members were studied as control subjects. It was found that EDS was present in 33.1% of DM1 patients. Severity of daytime sleepiness correlated with the degree of muscular impairment but not with age, gender, body mass index, age at onset of symptoms, duration of illness, and CTG repeat. DM1 patients reported a longer sleep period, a less restorative sleep, and more difficulty falling asleep, being alert in the morning and staying awake after meals than controls, but a similar incidence of narcolepsy auxiliary symptoms. Compared with DM1 patients without EDS, those with EDS reported greater hypnagogic hallucinations, and greater pain associated with nocturnal awakenings and in their legs upon morning awakenings. In sum, both DM1 patients with and without EDS exhibit characteristics of sleep duration and sleepiness comparable with those found in idiopathic hypersomnia. The severity of daytime sleepiness is weakly related to the extent of muscular impairment but not to CTG repeat.

Daytime variation in performance and tiredness/sleepiness ratings in patients with insomnia, narcolepsy, sleep apnea and normal controls

Abstract: Daytime tiredness or sleepiness and deficits in cognitive performance are common complaints in sleep disordered patients. Till now there are few studies comparing patients from different diagnostic groups of sleep disorders in the same experimental protocol. We studied the time course of cognitive functions and subjective alertness in a parallel group design with four groups of patients [narcolepsy, untreated or treated obstructive sleep apnea (OSA), or psychophysiological insomnia] and a control group of subjects without sleep complaints. Each group consisted of 10 subjects, matched for age and gender. After a night with polysomnography, subjects were studied for 10 h from 08:00 hours to 18:00 hours at 20 min intervals under standardized environmental conditions. Four psychological tests were applied, (1) a critical flicker fusion (CFF) test to measure optical fusion threshold (alertness); (2) a paper-and-pencil visual line tracking test (selective attention); (3) a visual analog scale (VAS) for tiredness/sleepiness; and (4) the Tiredness Symptoms Scale (TSS), a 14 items check list. Each test session lasted for 8 min, followed by a 12 min pause. The level and time course of cognitive performance and self-rating data were analysed with hierarchical linear mixed effects models. Cognitive tests showed decrements in alertness and selective attention in untreated patients with insomnia, narcolepsy, and sleep apnea. Narcoleptic patients and untreated OSA had a lower CFF threshold than controls, and for narcoleptic patients the time course differed from that of all other groups. In the visual tracking test the performance of all groups of patients was worse compared with normal controls. Self-rated tiredness/sleepiness was significantly more pronounced in the three groups of untreated patients than in control subjects.

Effect of cognitive behavioural therapy for insomnia on sleep architecture and sleep EEG power spectra in psychophysiological insomnia

Abstract: There is now an overwhelming preponderance of evidence that cognitive behavioural therapy for insomnia (CBT-I) is effective, as effective as sedative hypnotics during acute treatment (4-8 weeks), and is more effective in long term (following treatment). Although the efficacy of CBT-I in the treatment of chronic insomnia is well known, however there is little objective data on the effects of CBT-I on sleep architecture and sleep EEG power densities. The present study evaluated, first, subjective change in sleep quality and quantity, and secondly the modifications occurring in polysomnography and EEG power densities during sleep after 8 weeks of CBT-I. Nine free drug patients with psychophysiological insomnia, aged 33-62 years (mean age 47 +/- 9.7 years), seven female and two male participated in the study. Self-report questionnaires were administered 1 week before and 1 week after CBT-I, a sleep diary was completed each day 1 week before CBT-I, during CBT-I and 1 week after CBT-I. Subjects underwent two consecutive polysomnographic nights before and after CBT-I. Spectral analysis was performed the second night following 16 h of controlled wakefulness. After CBT-I, only scales assessing insomnia were significantly decreased, stages 2, REM sleep and SWS durations were significantly increased. Slow wave activity (SWA) was increased and the SWA decay shortened, beta and sigma activity were reduced. In conclusion CBT-I improves both subjective and objective sleep quality of sleep. CBT-I may enhance sleep pressure and improve homeostatic sleep regulation.

Sleep disorders in Taiwanese children with attention deficit/hyperactivity disorder.

Abstract: To assess obstructive sleep apnea syndrome (OSAS) and periodic limb movement disorder (PLMD) in children with attention deficit/hyperactivity disorder (ADHD) compared with a control group. The ADHD was diagnosed based on Diagnostic and Statistical Manual, version IV (DSM-IV) criteria on successively seen elementary school children aged 6-12 years referred to a psychiatric clinic for suspected ADHD. A standardized interview (Kiddie-SADS-E), parents and teacher questionnaires, neuropsychological testing, and nocturnal polysomnography were completed for each child. Eighty-eight children (77 boys) with ADHD and 27 controls were involved in the study. Fifty children with ADHD (56.8%) had an apnea-hypopnea index (AHI) >1 event h(-1) and 17 (19.3%) had an AHI >5 event h(-1). Nine children (10.2%) had a periodic limb movement index (PLMI) >5 events h(-1). There is one child with AHI >1 and none with a PLMI > 5 in the control group. In the test of variables of attention (TOVA), the response time was significantly worse in ADHD with sleep disorders than those without them. The child behavior checklist (CBCL) showed a significant difference between groups in the hyperactivity subscale. The diagnostic criteria for ADHD based on DSM-IV do not differentiate between children with or without sleep disorders. Evaluation of sleep disorders should be considered before starting drug treatment for ADHD.

Does cognitive dysfunction conform to a distinctive pattern in obstructive sleep apnea syndrome

Abstract: Summary Obstructive sleep apnea (OSA) is a recognized cause of cognitive dysfunction. By using a cross-sectional comparative study, we aimed to verify whether neuropsychological performance of untreated OSA patients conforms to a distinctive pattern. Forty-nine newly diagnosed, untreated OSA patients, 27 with multi-infarctual dementia (MID), 31 with mild to moderate dementia of Alzheimer type (DAT) and 63 with severe chronic obstructive pulmonary disease (COPD), all free from major comorbid dementing conditions were chosen for the study. The groups were matched for age and education. We found a bimodal distribution of cognitive performance in OSA group, which was therefore divided into two clusters having better (OSAb, n = 35) and worse (OSAw, n = 14) performance on a battery of 10 cognitive indexes. Cognitive performances of OSAb, OSAw, MID, DAT and COPD were compared by discriminant analysis. OSAb performed better than OSAw in all but one test. Deductive thinking and verbal attainment were more severely impaired in OSAw than in COPD patients. Constructive ability, deductive thinking and both verbal attainment and immediate memory were comparably impaired in OSAw and DAT. The mean neuropsychological scores of OSAw and MID were comparable, but 71% of OSAw patients had a distinctive cognitive profile, i.e. a group specific pattern of cognitive dysfunction, according to discriminant analysis. One of four newly diagnosed OSA patients had a severe and distinctive neuropsychological dysfunction mainly involving inductive and deductive thinking, and constructive ability. Some analogy with cognitive pattern of MID suggests that a mainly subcortical damage underlies this dysfunction.

Is there a specific polysomnographic sleep pattern in children with attention deficit/hyperactivity disorder?

Abstract: The aim of the study was to characterize the sleep pattern in children with attention deficit/hyperactivity disorder (ADHD). By means of polysomnography (PSG), sleep patterns were studied in 17 unmedicated preadolescent boys rigorously diagnosed with ADHD and 17 control boys precisely matched for age and intelligence. Although ADHD children did not display a general sleep alteration, major PSG data showed a significant increase in the duration of the absolute rapid eye movement (REM) sleep and the number of sleep cycles in ADHD group when compared with controls. In addition, REM sleep latency tended to be shorter in ADHD children. These results suggest that in ADHD children, a forced REM sleep initiation may produce a higher incidence of sleep cycles and may also contribute to an increased duration of the absolute REM sleep. The overall pattern of the findings implies that a forced ultradian cycling appears characteristic for the sleep in ADHD children, which may be related to alterations of brain monoamines and cortical inhibitory control accompanying the ADHD psychopathology.

Waking up properly: is there a role of thermoregulation in sleep inertia?

Abstract: We assume that alertness should be highest at the end of a sleep episode: it is not. There is always sleep inertia upon awakening, which can last minutes to hours, and whose underlying physiological mechanisms are largely unknown. Previously, we had found a functional relationship between the degree of distal vasodilatation (as measured by the distal-proximal skin temperature gradient (DPG) and sleepiness (as measured by subjective ratings), promoting rapid sleep onset. This led us to hypothesize that the dissipation of sleep inertia (sleepiness) would be associated with reverse thermoregulatory mechanisms, i.e. distal vasoconstriction. In two sets of experiments with either a nocturnal sleep episode (study 1) or an afternoon nap (study 2) we could show that vasodilatation of hands and feet increased after lights off and that this was reversed after lights on. The time course of the DPG was significantly and positively correlated with subjective sleepiness (KSS), reflecting similar temporal relationships in both studies 1 and 2. The extremities cooled at a rate very closely parallel to the decay of sleepiness [time constants for the exponential decline calculated for study 2: DPG, 0.286 +/- 0.048 h versus KSS, 0.332 +/- 0.050 h; NS], indicating redistribution of heat from the shell to the core during dissipation of sleepiness. There was no statistical evidence that the time course of sleep inertia and its thermophysiological correlates depend on sleep structure prior to awakening. The symmetry between the thermoregulatory processes initiating sleepiness and those dissipating it is striking. In order to directly test our hypothesis, further studies with thermophysiological interventions (e.g. cooling the extremities) are needed.

Changes in fronto-posterior functional coupling at sleep onset in humans.

Abstract: SUMMARY The aim of this study was to assess the functional coupling between anterior andposterior areas as induced by the sleep onset process. The functional coupling wasindexed by an analysis of spectral coherence and directed transfer function (DTF) fromelectroencephalographic (EEG) data. As it has been reported that more anterior areasfirst synchronize sleep EEG activity, we hypothesized a fronto-posterior direction of thecortical functional coupling during the sleep onset process. Ten normal right-handedmale students slept for two-nights (one adaptation, one baseline) in the laboratory, withstandard polysomnographic recordings. Spectral coherence and DTF were computedon data recorded by anterior (FzA 1 ) and posterior (PzA 1 , OzA 1 ) derivations. EEGcoherence at the delta/theta band was higher during the presleep period than the sleeponset period, while EEG coherence at the alpha band was higher during the sleep onsetperiod than the presleep period. The DTF findings indicated a prevalence of theoccipital-to-frontal information flow at delta/theta and alpha bands during the presleepperiod and a prevalence of the frontal-to-parieto-occipital information flow at all bandsduring the sleep onset period. The coherent pattern of changes in EEG coherence and inDTF values at sleep onset lends further support to the notion of sleep as a local process,showing that the sleep onset process is subserved by the functional coordination of acortical fronto-posterior network. In this network, prefrontal areas may play a leadingrole in the propagation of synchronizing signals conveyed at frequencies spanning deltato beta rhythms.keywords directed coherence, directed transfer function, electroencephalographiccoherence, sleep onset, spectral analysis

Counterpointing the functional role of the forebrain and of the brainstem in the control of the sleep-waking system.

Abstract: This paper reviews the lifetime contributions of the author to the field of sleep-wakefulness (S-W), reinterprets results of the early studies, and suggests new conclusions and perspectives. Long-term cats with mesencephalic transection show behavioral/polygraphic rapid eye movement sleep (REMS), including the typical oculo-pupillary behavior, even when the section is performed in kittens prior to S-W maturation. REMS can be induced as a reflex. Typical non-rapid eye movement S (NREMS) is absent and full W/arousal is present only after a precollicular section. The isolated forebrain (IF) rostral to the transection exhibits all features of W/arousal and NREMS [with electroencephalographic (EEG) spindles and delta waves], arousal to olfactory stimuli, and including the appropriate oculo-pupillary behaviors. These features also mature normally after neonatal transection. REMS is absent from the IF. After deprivation there is NREMS pressure and rebound in the IF, but the decerebrate cat only shows pressure for REMS. Most IF reactions to pharmacologic agents are within expectations, except for the tolerance/withdrawal effects of long-term morphine use which are absent. In contrast, these effects are supported by the brainstem (i.e. seen in the decerebrate cat). In cats with ablation of the telencephalon, or diencephalic cats, delta waves are absent in the thalamus. EEG thalamic spindle waves are seen triggering S for only 4-5 days after ablation. Therefore, true NREMS is absent in chronic diencephalic cats although pre- and postsomniac behaviors persist. These animals are hyperactive and show a pronounced, permanent insomnia; however, a low dose of barbiturate triggers a dramatic REMS/atypical NREMS rebound. Cats without the thalamus (athalamic cats), initially show a dissociation between behavioral hyperactivity/insomnia and the neocortical EEG, which for 15-20 days exhibits only delta and slower oscillations. Fast, low-voltage W rhythms appear later on, first during REMS, but spindle waves and S postures are absent from the start, such that these cats also display only atypical NREMS. Athalamic cats also show barbiturate-sensitive insomnia. Cats with ablation of the frontal cortices or the caudate nuclei remain permanently hyperactive. They also show a mild, but significant hyposomnia, which is permanent in afrontal cats, but lasts for about a month in acaudates. The polygraphic/behavioral features of their S-W states remain normal. We conclude and propose that: (a) the control of the S-W system is highly complex and distributed, but is organized hierarchically in a well-defined rostro-caudal manner; the rostral-most or highest level (telencephalon), is the most functionally complex/adaptative and regulates the lower levels; the diencephalic/basal forebrain, or middle level, has a pivotal role in inducing switching between S and W and in coordinating the lowest (brainstem) and highest levels; (b) W can occur independently in both the forebrain and brainstem, but true NREMS- and REMS-generating mechanisms exist exclusively in the forebrain and brainstem, respectively; (c) forebrain and brainstem S-W processes can operate independently from each other and are preprogrammed at birth; this helps understanding normal and abnormal polygraphic/behavioral dissociations in humans and normal dissociations/splitting in aquatic mammals; (d) NREMS homeostasis is present in the IF, but only REMS pressure after deprivation persists in the decerebrate cat; (e) the thalamus engages in both NREMS and W; (f) insomnia in diencephalic cats is the result of an imbalance between antagonistic W- and S-promoting cellular groups in the ventral brain (normally modulated by the telencephalon); (g) the EEG waves, which are signature for each S-W state, appear to truly drive the concomitant behaviors, e.g. a hypothetical human IF could alternate between behavioral NREMS and W/arousal/awareness; (h) a role for REMS is to keep the individual sleeping at the end of the self-limiting NREMS periods. The need for accelerating research on telencephaling NREMS periods. The need for accelerating research on telencephalic S-W processes and downstream control of the lower S-W system levels is emphasized.

Does frequency of nocturnal urination reflect the severity of sleep-disordered breathing?

Abstract: Nocturia is an often-described symptom of sleep-disordered breathing (SDB). The aim of our study was to determine the frequency of nocturnal urination among patients with different severity of SDB and to find out whether frequency of nocturnal urination reflects the severity of disease. A retrospective chart review was conducted among 1075 subjects of suspected SDB. Nocturia was assessed using standard questionnaire evaluating a frequency of nocturnal urination. Subjects were divided into four groups of SDB based on the polysomnographic evaluation. In primary snoring group, 51% subjects did not complain nocturia, 28% subjects reported one time, 16% subjects reported two to three times and 5% subjects reported more than three times urination per night. Among patients with mild obstructive sleep apnea syndrome (OSAS), nocturnal urination was not reported by 36% and was reported one time by 34%, two to three times by 15%, more than 3 times by 15%. The corresponding frequencies among patients with moderate OSAS were 40, 31, 17 and 12%, and with severe OSAS were 23, 22, 23 and 32%, respectively. The severe OSA group was significantly different from other groups as regards the frequency of nocturnal urination (P < 0.001) while other OSA groups did not show any significance. Nocturnal urination of more than three times was significantly more reported by severe OSA patients ( P < 0.001) (positive predictive value = 0.71, negative predictive value = 0.62).

Sleep deprivation in honey bees.

Abstract: Rest at night in forager honey bees (Apis mellifera) meets essential criteria of sleep. This paper reports the effect of a 12-h total sleep deprivation (SD) by forced activity on the behaviour of these animals. The behaviour of sleep-deprived animals is compared with that of control animals under LD [periodic alternation between light (L) and darkness (D)] 12 : 12 hours. SD for 12 h during the first D period resulted in a significant difference with respect to the parameter 'hourly amount of antennal immobility' between sleep-deprived and control animals during the remaining L and D periods. This difference did not occur in the L period following the deprivation night, but rather it became obvious at the beginning of the following D period. The increase of the amount of antennal immobility in sleep-deprived bees was accompanied by an increase of the duration of episodes of antennal immobility. Moreover, the latency from 'lights off' to the first episode of antennal immobility lasting 20 s or longer ('deep sleep latency') tended to be shorter in sleep-deprived than in control animals. Disturbing the bees during the day (L period) did not result in such differences between disturbed and control animals. Highest reaction thresholds in sleeping honey bees occur during long episodes of antennal immobility. We therefore conclude that honey bees compensate a sleep deficit by intensification (deepening) of the sleep process and thus that sleep in honey bees, like that in other arthropods and mammals, is controlled by regulatory mechanisms.

The effects of bright-light therapy on actigraphical measured sleep last for several weeks post-treatment. A study in a nursing home population.

Abstract: We investigated the time-course of nocturnal actigraphic measures, following the termination of bright-light therapy for sleep disturbances in demented nursing home patients. From an earlier study, 11 nursing home patients (86 +/- 9 years, Mini-Mental Status Examination score 12 +/- 4) with actigraphically measured sleep efficiency < 85%, were recruited to morning bright-light treatment (6000-8000 lux) 2 h per day for 14 days. Actigraphic measures were registered at pretreatment, treatment and at four monthly post-treatment periods. Each actigraphic recording period consisted of seven consecutive days. Sleep improved substantially with treatment; sleep efficiency increased from 73% to 86% and total nocturnal wake time was reduced by nearly 2 h. During the 16 weeks post-treatment period, actigraphic measures gradually returned to pretreatment levels. Sleep efficiency remained significantly higher than the pretreatment level 4 weeks after treatment termination. Sleep onset latency remained significantly reduced up until 12 weeks post-treatment. This study supports previous findings of beneficial effects of bright-light therapy for sleep disturbances in demented nursing home patients. Furthermore, these results are the first to suggest that post-treatment effects of short-term bright-light therapy may last longer than previously assumed.

Experimentally induced arousals during sleep: a cross-modality matching paradigm.

Abstract: Micro-arousals occur spontaneously or in response to exogenous and endogenous sensory input during sleep. The function of micro-arousals remains unclear, for example, whether it reflects a disturbance or a preparatory response to environmental changes. The goal of this study was to assess arousal responsiveness when two types of sensory stimulations were used: auditory (AD) alone and the addition of a vibrotactile (VT) sensation. Ten normal sleepers participated in three nights of polygraphic recordings. The first night was for habituation and to rule out sleep disorders, and the second to collect baseline sleep data. During the third night, AD and VT + AD stimuli, with three levels of intensities for auditory and vibratory signals, were randomly given to induce arousal responses in sleep stages 2, 3 and 4 and rapid eye movement (REM). The frequency of the arousal responses increased with stimulus intensity for all sleep stages and was lowest in stages 3 and 4. In non-REM (NREM) sleep, combined VT + AD stimulation induced more frequent and more intense arousal responses than AD alone. In REM sleep, more frequent micro-arousals rather than awakenings were triggered by combined stimulations. In stage 2, the response rate of total induced K-complexes did not differ between both types of stimulations while more K-complexes followed by arousals were evoked by the combined VT + AD stimulation than by the AD alone. The induced arousals were associated with an increase in heart rate in all sleep stages. An increase in suprahyoid muscle tone was observed in NREM sleep only, REM being not associated with a rise in muscle tone following experimental stimulation. Most leg and body movements occurred in response to induced awakenings. These results suggest that the cross-modality sensory stimuli triggered more arousal responses in comparison with single-modality stimuli. In an attempt to wake a sleeping subject, the addition of a tactile stimulation, such as shaking the shoulder, is an effective strategy that increases the arousal probability.

The effects of sleep debt and monotonous work on sleepiness and performance during a 12-h dayshift.

Abstract: Summary The study examined the effects of the amount of preceding sleep and work pace on sleepiness and cognitive performance during a 12-h dayshift. Twelve process operators (aged 28–56 years) completed a study with four single 12-h dayshifts and preceding night sleep in the laboratory. A simulated distillation process served as a work task. The 12-h shifts differed from each other in terms of the amount of preceding night sleep (23:00–06:30 hours or 2:30–6:30 hours) and work pace (slow or fast). All shifts contained four work simulation sessions of 1.5 h, and each of them included a 15-min alarm session. Cognitive performance was also measured with a 10-choice reaction time test and a mental subtraction test. Objective sleepiness was measured with a continuous electroencephalography/electro-oculography (EEG/EOG) recording during the work periods and with a sleep latency test. Subjective sleepiness at work was measured with the Karolinska Sleepiness Scale. Sleep debt increased the proportion of EEG/EOG-defined and subjective sleepiness at work, but did not impair work or test performance. The fatiguing effect of monotonous work as indicated by EEG/EOG-defined sleepiness was comparable with the effect of sleep debt. The alarm epochs in the middle of monotonous work temporarily decreased EEG/EOG-defined sleepiness. Sleep debt or monotonous work did not have a significant effect on the results of the sleep latency test. None of the sleepiness or performance measures indicated the impairment of a subject's functional capacity at the end of the 12-h shift. Our results suggest that monotonous work is at least as harmful as moderate sleep debt for alertness at work. The results support the view that the last hours of a single 12-h dayshift with frequent pauses are not associated with an increase in sleepiness or performance errors.

The 24-h growth hormone rhythm in men: sleep and circadian influences questioned.

Abstract: The 24-h rhythm of growth hormone (GH) is thought to be controlled primarily by sleep processes with a weak circadian component. This concept has been recently questioned in sleep-deprived persons. To test the notion of a high sleep-dependency of GH release, we established simultaneous 24-h rhythms of GH and melatonin, a circadian marker, in night workers who form a model for challenging sleep and circadian processes. Ten day-active subjects and 11 night workers were studied during their usual sleep-wake schedule, with sleep from 23:00 to 07:00 hours and 07:00 to 15:00 hours, respectively. Experiments were conducted in sleep rooms under continuous nutrition, bed rest, and dim light. Melatonin and GH were measured every 10 min over 24 h. In day-active subjects, melatonin and GH showed the well-known 24-h profiles, with a major sleep-related GH pulse accounting for 52.8 +/- 3.5% of the 24-h GH production and the onset of the melatonin surge occurring at 21:53 hours +/- 18 min. In night workers, melatonin showed variable circadian adaptation, with the onset of secretion varying between 21:45 and 05:05 hours. The sleep-related GH pulse was lowered, but the reduction was compensated for by the emergence of large individual pulses occurring unpredictably during waking periods, so that the total amount of GH secreted during the 24 h was constant. One cannot predict the degree of GH adaptation from the highly variable melatonin shift. These results argue against the concept that sleep processes exert a predominant influence on GH release whatever the conditions. When sleep and circadian processes are misaligned, the blunting of the sleep-related GH pulse is counteracted, as in sleep-deprived persons, by a compensatory mechanism promoting GH pulses during wakefulness.

Analysis of postarousal EEG activity during somnambulistic episodes

Abstract: Early studies found that electroencephalographic (EEG) recordings during somnambulistic episodes were characterized by a combination of alpha, theta, and delta frequencies, without evidence of clear wakefulness. Three postarousal EEG patterns associated with slow-wave sleep (SWS) arousals were recently identified in adults with sleepwalking and sleep terrors. The goal of the present study was to evaluate the distribution of these postarousal EEG patterns in 10 somnambulistic patients (three males, seven females, mean age: 25.1, SD: 4.1) evaluated at baseline and following 38 h of sleep deprivation. A total of 44 behavioral arousals were recorded in the laboratory; seven episodes at baseline (five from SWS, two from stage 2 sleep) and 37 episodes during recovery sleep (30 from SWS, seven from stage 2 sleep). There was no significant difference in the distribution of postarousal EEG patterns identified during baseline and recovery sleep. One pattern, comprised of diffuse rhythmic and synchronous delta activity, was preferentially associated with relatively simple behavioral episodes but did not occur during episodes from stage 2 sleep. Overall, delta activity was detected in 48% of the behavioral episodes from SWS and in 22% of those from stage 2. There was no evidence of complete awakening during any of the episodes. The results support the view of somnambulism as a disorder of arousal and suggest that sleepwalkers' atypical arousal reactions can manifest themselves in stage 2 sleep in addition to SWS.

Comparison of the maintenance of wakefulness test (MWT) to a modified behavioral test (OSLER) in the evaluation of daytime sleepiness.

Abstract: The objectives were to evaluate the correlation between sleep onset as defined by the Oxford sleep resistance (OSLER) test and by simultaneous electroencephalography (EEG) and to determine the correlation between sleep latencies measured by the OSLER test and maintenance of wakefulness test (MWT) performed on the same day. This was a prospective, cross-sectional study carried out in a tertiary-care university-based sleep laboratory. Participants were 11 consecutive subjects presenting to the sleep center with clinical indications for nocturnal polysomnography and MWT. The interventions included MWT and OSLER test. Mean sleep latencies for the OSLER and MWT in each subject were closely correlated (ICC = 0.94, [Intra-class correlation]P < 0.05). Sleep latency by OSLER and simultaneous measurement of EEG also had excellent agreement (ICC = 0.91) with a bias of -0.97 min. The OSLER test is a practical and reliable tool for evaluating daytime sleepiness when compared with the MWT. No obvious systematic adaptation was seen during sequential OSLER test performance. Given its portability and minimal technical requirements, the OSLER test may be useful for large-scale applications in the evaluation of daytime wakefulness and vigilance.

Stimulus-induced brain lactate: effects of aging and prolonged wakefulness

Abstract: Summary Both aging and sleep deprivation disturb the functions of the frontal lobes. Deficits in brain energy metabolism have been reported in these conditions. Neurons use not only glucose but also lactate as their energy substrate. The physiological response to elevated neuronal activity is a transient increase in lactate concentrations in the stimulated area. We have previously shown that cognitive stimulation increases brain lactate. To study the effect of prolonged wakefulness on the lactate response we designed an experiment to assess brain lactate levels during a 40-h sleep deprivation period in young (19–24 years old; n = 13) and in aged (60–68 years old; n = 12) healthy female volunteers. Brain lactate levels were assessed with proton MR-spectroscopy (1H MRS) during the performance of a silent word generation task. The 1H MRS voxel location was individually selected, using functional magnetic resonance imaging, to cover the activated area in the left frontal lobe. The degree of sleepiness was verified using vigilance tests and self-rating scales. In the young alert subjects, the silent word generation test induced a 40% increase in lactate, but during the prolonged wakefulness period this response disappeared. In the aged subjects, the lactate response could not be detected even in the alert state. We propose that the absence of the lactate response may be a sign of malfunctioning of normal brain energy metabolism. The behavioral effects of prolonged wakefulness and aging may arise from this dysfunction.