Showing papers in "Journal of Sleep Research in 1997"

Psychophysiological insomnia: the behavioural model and a neurocognitive perspective.

Abstract: A number of paradoxes are apparent in the assessment and treatment of psychophysiological insomnia and sleep state misperception. Three of these paradoxes exist as discrepancies between polysomnographic (PSG) measures and the subjective impressions regarding sleep quality and quantity. The remaining incongruity exists largely within the objective domain. In the case of subjective-objective discrepancies, patients with insomnia: (1) frequently identify themselves as having been awake when awakened from PSG defined sleep; (2) tend to overestimate sleep latency and underestimate total sleep time as compared with PSG measures; (3) appear to derive more benefit from pharmacotherapy that can be explained by objective gains. The remaining paradox pertains to the observation that hypnotic medications, by and large, do not normalize sleep architecture or produce a more 'sleep-like' EEG. In this paper, we review possible explanations for these various paradoxes, introduce a new perspective and suggest possible research avenues. The model introduced is based on the observation that beta and/or gamma activity (which have been found to be associated with cognitive processes) is enhanced in insomnia at or around sleep onset. We propose that this kind of high frequency EEG activity may interfere with the normal establishment of sleep onset-related mesograde amnesia. As a result, the patient with insomnia maintains a level of information and/or memory processing that blurs the phenomenological distinction between sleep and wakefulness and influences retrospective judgments about sleep initiation and duration.

Circadian rhythms in human performance and mood under constant conditions

Abstract: This study explored the relationship between circadian performance rhythms and rhythms in rectal temperature, plasma cortisol, plasma melatonin, subjective alertness and well-being. Seventeen healthy young adults were studied under 36 h of 'unmasking' conditions (constant wakeful bedrest, temporal isolation, homogenized 'meals') during which rectal temperatures were measured every minute, and plasma cortisol and plasma melatonin measured every 20 min. Hourly subjective ratings of global vigour (alertness) and affect (well-being) were obtained followed by one of two performance batteries. On odd-numbered hours performance (speed and accuracy) of serial search, verbal reasoning and manual dexterity tasks was assessed. On even-numbered hours, performance (% hits, response speed) was measured at a 25-30 min visual vigilance task. Performance of all tasks (except search accuracy) showed a significant time of day variation usually with a nocturnal trough close to the trough in rectal temperature. Performance rhythms appeared not to reliably differ with working memory load. Within subjects, predominantly positive correlations emerged between good performance and higher temperatures and better subjective alertness; predominantly negative correlations between good performance and higher plasma levels of cortisol and melatonin. Temperature and cortisol rhythms correlated with slightly more performance measures (5/7) than did melatonin rhythms (4/7). Global vigour correlated about as well with performance (5/7) as did temperature, and considerably better than global affect (1/7). In conclusion: (1) between-task heterogeneity in circadian performance rhythms appeared to be absent when the sleep/wake cycle was suspended; (2) temperature (positively), cortisol and melatonin (negatively) appeared equally good as circadian correlates of performance, and (3) subjective alertness correlated with performance rhythms as well as (but not better than) body temperature, suggesting that performance rhythms were not directly mediated by rhythms in subjective alertness.

Sleep and morningness-eveningness in the 'middle' years of life (20-59 y).

Abstract: The following four issues were assessed in a group of 110 adults between the age of 20 and 59y: (1) the effect of age (regarded as a continuous variable) on polysomnographic sleep characteristics, habitual sleep-diary patterns, and subjective sleep quality; (2) the effects of age on morningness-eveningness; (3) the effects of morningness-eveningness on sleep, after controlling for the effects of age; and (4) the role of morningness-eveningness as a mediator of the age and sleep relationship. Increasing age was related to earlier habitual waketime, earlier bedtime, less time in bed and better mood and alertness at waketime. In the laboratory, increasing age was associated with less time asleep, increased number of awakenings, decreased sleep efficiency, lower percentages of slow-wave sleep (SWS) and rapid eye movement (REM) sleep, higher percentages of Stage 1 and 2, shorter REM latency and reduced REM activity and density. Increasing age was also associated with higher morningness scores. After controlling for the effects of age, morningness was associated with earlier waketime, earlier bedtime, less time in bed, better alertness at waketime, less time spent asleep, more wake in the last 2 h of sleep, decreased REM activity, less stage REM (min and percentage), more Stage 1 (min and percentage) and fewer minutes of Stage 2. For one set of variables (night time in bed, waketime, total sleep time, wake in the last 2 h of sleep and minutes of REM and REM activity), morningness-eveningness accounted for about half of the relationship between age and sleep. For another set of variables (bedtime, alertness at waketime, percentages of REM and Stage 1), morningness-eveningness accounted for the entire relationship between age and sleep. In conclusion, age and morningness were both important predictors of the habitual sleep patterns and polysomnographic sleep characteristics of people in the middle years of life (20-59 y).

Fronto-occipital EEG power gradients in human sleep.

Abstract: The brain topography of power spectra along the antero-posterior (A-P) axis was studied in the all-night human sleep EEG. Spectra (0.25 - 25.0 Hz) were computed for an anterior (A; F3-C3), a middle (M; C3-P3) and a posterior (P; P3-O1) bipolar derivation, and the spectral gradients between two adjacent derivations were expressed by power ratios (A/M and M/P). At NREM-REM sleep transitions a power shift from A to M was present over almost the entire frequency range, while the direction of shifts between M and P differed between frequency bands. Within NREM sleep, frequency specific power gradients were present: In the low delta band power in both A (0.25 Hz bin) and P (0.25-1.0 Hz bins) was higher than in M. In the 4-9 Hz range the relation was A > M > P, and in the 15 - 25 Hz range power was largest in M. Power in the spindle frequency range was highest at 11.75 Hz in M, and at 13.5 - 13.75 Hz in A. Topographical differences were seen also in the temporal changes of power across and within NREM sleep episodes. Whereas NREM sleep power in the 2-Hz bin was higher in A than in M in the first episode, this difference vanished in the course of the night. This result points to a specific involvement of frontal parts of the cortex in sleep homeostasis. The regional differences in sleep EEG spectra indicate that sleep is not only a global phenomenon but also a local brain process with a different regional involvement of neuronal populations.

A behavioural test to assess daytime sleepiness in obstructive sleep apnoea

Abstract: Daytime sleepiness is an important symptom of obstructive sleep apnoea syndrome (OSAS). The standard tests for its objective quantification use EEG recordings, and are time consuming and expensive, which makes them difficult to use for large studies. This study assesses the ability of a simple test of sustained 'wakefulness' to discriminate the excessive somnolence of severe symptomatic obstructive sleep apnoea from normality, and compares its results to the traditional EEG based Maintenance of Wakefulness Test (MWT). Ten subjects (7M 3F) with severe sleep apnoea (> 4% SaO2 dip rate median 32.7 (90% central range 9.7-65.6)) and symptoms of daytime sleepiness, (Epworth Sleepiness Score (ESS)17(10-24)) and 10 normal subjects (4M 6F, ESS 3.5(1-8)) were studied. The MWT and the behavioural test (Oxford SLEep Resistance test - OSLER test) were performed on each subject in random order on 2 separate days. The protocol for both tests was the same with 4 X 40 min sleep resistance challenges throughout the day while sound isolated in a darkened room. During the OSLER test subjects were asked to press a switch in response to a light emitting diode (LED), which was lit for 1 s in every three. Both the switch and the light were connected to a computer that stored both the number of times the light was illuminated and whether a correct response was made. The OSLER test discriminated the normal subjects from the sleep apnoea group (mean sleep latency (min) normal group 39.8, OSA group 10.5) as well as the traditional MWT (normal group 38.1 OSA group 7.3) and was much simpler to administer. This test has the advantage that sleep onset is defined objectively and automatically as a failure to respond to the light, rather than from EEG interpretation, which is inevitable partly subjective. This technique may provide a simple and robust method of objectively quantifying daytime sleepiness for large studies.

Comparison of three measures of quality of life outcome in the evaluation of continuous positive airways pressure therapy for sleep apnoea

Abstract: Treatment of obstructive sleep apnoea (OSA) with nasal continuous positive airway pressure (NCPAP) has become a standard treatment since its introduction in 1981. Following such treatment the apnoeas disappear, sleep quality improves as apparently do daytime symptoms of sleepiness. Sleepiness is an unusual symptom and its impact on conventional indices of quality of life has rarely been measured. To allow comparison of NCPAP therapy with treatments for other conditions, measurements of quality of life before and after treatment using standard techniques are required. It is not clear which of the standard measures is most suited to measuring the health gain from nasal NCPAP, and indeed whether the disability of excessive sleepiness is included in all such measures. This study looks at three well recognized quality of life measures in OSA, before and after NCPAP therapy; the Short Form 36 (SF-36), Functional Limitations Profile (FLP), and the EuroQol (EQ-5D). The results were compared with data from normal populations. One hundred and eight patients with OSA undergoing a therapeutic assessment of NCPAP completed the three quality of life questionnaires before and 5 weeks after commencing treatment. Over 90 subjects completed all sections of the three measures on both occasions. The SF-36 revealed substantial adverse effects on subjective health of OSA and that NCPAP treatment produced dramatic positive effects. For example, the effect sizes (difference in score, divided by SD of baseline score) in the Energy/Vitality dimension was 0.98 and for the overall Mental and Physical Component Scores, 0.76 and 0.57, respectively: an effect size over 0.5 is considered moderate and over 0.8 as large. The FLP data showed similar pre treatment decrements in quality of life and substantial improvements following NCPAP. The changes with treatment in the majority of the dimensions from both the SF-36 and FLP were statistically significant (P < 0.01). In contrast the EQ-5D did not show significant improvements with therapy, presumably because of its failure to measure the aspects of quality of life related to severe sleep fragmentation and daytime sleepiness. In conclusion, this study has clearly shown considerable decrements in quality of life in patients with OSA, similar to other chronic disabling conditions. Furthermore, NCPAP therapy returns patients to a quality of life similar to the normal population.

Topographic distribution of sleep spindles in young healthy subjects

Abstract: The application of an automatic sleep spindle detection procedure allowed the documentation of the topographic distribution of spindle characteristics, such as number, amplitude, frequency and duration, as a function of sleep depth and of recording time. Multichannel all-night EEG recordings were performed in 10 normal healthy subjects aged 20-35 years. Although the interindividual variability in the number of sleep spindles was very high (2.7 +/- 2.1 spindles per minute stage 2 sleep), all but two subjects showed maximal spindle activity in centro-parietal midline leads. Moreover, this topography was seen in all sleep stages and changed only slightly--to a more central distribution--towards the end of the night. On the other hand, slow (11.5-14 Hz) and fast (14-16 Hz) spindles showed a completely different topography, with slow spindles distributed anteriorly and fast spindles centro-parietally. The number of sleep spindles per min was significant depending on sleep stages, with the expected highest occurrence in stage 2, and on recording time, with a decrease in spindle density from the beginning towards the end of the night. However, spindle amplitude, frequency and individual duration was not influenced by sleep depth or time of the night.

Objective components of individual differences in subjective sleep quality.

Abstract: The relation between subjective and objective (polysomnography) is of obvious interest in understanding sleep. The aim of the present study was to examine the item structure of the Karolinska Sleep Diary (KSD), and the covariation between KSD and sleep-stage variables, with cross-sectional (inter-individual) data obtained in natural conditions. Thirty-seven subjects had a polysomnography prior to a work day. After rising they completed the Karolinska Sleep Diary. A factor analysis of the diary yielded two factors: (1) a sleep-quality index (SQI) related to the initiation and maintenance of sleep, and (2) a second factor related to difficulties waking-up and to whether sleep was recuperative and sufficient. The strongest predictors (multiple regression) of the sleep quality index was slow-wave sleep (SWS) and sleep efficiency [and variables related to sleep continuity total sleep time (TST) and the amount of stage 0]. The obtained results were in agreement with previous laboratory findings. It was concluded that sleep quality seems to be a matter of depth of sleep and sleep continuity.

Good sleep--its timing and physiological sleep characteristics.

Abstract: SUMMARY The present study used short sleep episodes to explore the relation between subjective sleep quality, timing and physiological content of sleep. Eight subjects participated in 18 4-h sleep episodes to provide 4, 8, and 12 h of prior time awake before bedtimes at six different times of day in a sleep laboratory insulated from environmental disturbances. The results were analysed by ANOVAs and multiple regression techniques. Subjective sleep quality, calmness of sleep, ease of falling asleep, ability to ‘sleep through’, number of awakenings, and sleep latency showed a significant pattern of ‘better’ sleep with increasing prior time awake and with closeness to the circadian minimum (nadir) of rectal temperature (morning hours). ‘Ease of awakening’ in contrast, ‘decreased’ with increasing time awake and with closeness to the nadir/ morning hours. Multiple regression analysis showed that subjective sleep quality was predicted by subjective calmness of sleep and ease of falling asleep, among the subjective measures, and by total sleep time (TST) and slow-wave sleep (SWS – stages 3 +4) among the physiological sleep measures. The subjective ease of awakening was predicted by slow-wave sleep (negatively) and the circadian maximum of rectal temperature. The results indicate that the duration of wakefulness prior to sleep and the timing of sleep determine its physiological expression, which in turn determines its subjective impression.

Combination of bright light and caffeine as a countermeasure for impaired alertness and performance during extended sleep deprivation.

Abstract: Effects of four conditions (Dim Light-Placebo, Dim Light-Caffeine, Bright Light-Placebo and Bright Light-Caffeine) on alertness, and performance were studied during the night-time hours across 45.5 h of sleep deprivation. Caffeine (200 mg) was administered at 20.00 and 02.00 hours and bright-light exposure (> 2000 lux) was from 20.00 to 08.00 hours each night. The three treatment conditions, compared to the Dim Light-Placebo condition, enhanced night-time performance. Further, the combined treatment of caffeine and all-night bright light (Bright Light-Caffeine) enhanced performance to a larger degree than either the Dim Light-Caffeine or the Bright Light-Placebo condition. Beneficial effects of the treatments on performance were largest during the early morning hours (e.g. after 02.00 hours) when performance in the Dim Light-Placebo group was at its worst. Notably, the Bright Light-Caffeine condition was able to overcome the circadian drop in performance for most tasks measured. Both caffeine conditions improved objective alertness on the Maintenance of Wakefulness Test. Taken together, the above results suggest that the combined treatment of bright light and caffeine provides an effective intervention for enhancing alertness and performance during sleep loss. Language: en

Slow-wave sleep: do young adult men and women age differently?

Abstract: The differential effects of ageing on polysomnographic and EEG spectral characteristics of sleep were explored in men and women between the ages of 20 and 40. Men and women in their twenties were found to have similar percentages of slow-wave sleep (SWS) (% Stage 3 and 4) and mean EEG slow wave activity (quantified by spectral analysis). Significant reductions in the percentage of SWS and mean slow wave activity over the night occurred in men during their thirties but not in the women. This suggests that gender difference in SWS may emerge between age 30 and 40 in young adults. Men in this sample were also found to have significant increases in Stage 2 sleep, and decreases in REM sleep time, REM activity, REM density and REM intensity. No significant effects of age were found for women in any visually scored sleep variables. Both men and women had age related reductions in spectral power in the spindle frequencies. Taken together, these findings suggest that the sleep of men and women over age 20-40 may age differently.

The alteration of human sleep and circadian rhythms during spaceflight

Abstract: Numerous anecdotes in the past suggest the concept that sleep disturbances in astronauts occur more frequently during spaceflight than on ground. Such disturbances may be caused in part by exogenous factors, but also an altered physiological state under microgravity may add to reducing sleep quality in a spacecraft. The present investigation aims at a better understanding of possible sleep disturbances under microgravity. For the first time, experiments were conducted in which sleep and circadian regulation could be simultaneously assessed in space. Four astronauts took part in this study aboard the Russian MIR station. Sleep was recorded polygraphically on tape together with body temperature. For a comparison, the same parameters were measured during baseline periods preceding the flights. The circadian phase of body temperature was found to be delayed by about 2 h in space compared with baseline data. A free-run was not observed during the first 30 d in space. Sleep was shorter and more disturbed than on earth. In addition, the structure of sleep was significantly altered. In space, the latency to the first REM episode was shorter, and slow-wave sleep was redistributed from the first to the second sleep cycle. Several mechanisms may be responsible for these alterations in sleep regulation and circadian phase. Most likely, altered circadian zeitgebers on MIR and a deficiency in the process S of Borbely's sleep model cause the observed findings. The change in process S may be related to changes in physical activity as a result of weightlessness.

Interactions between sleep and sensory physiology

Abstract: The processing of sensory information is definitely present during sleep, however, profound modifications occur. All sensory systems reviewed (visual, auditory, vestibular, somesthetic and olfactory) demonstrate some influence on sleep and, at the same time, sensory systems undergo changes that depend on the sleep or waking state of the brain. Thus, different sensory modalities encoded by their specific receptors and pathways may not only alter the sleep and waking physiology, but also the sleeping brain imposes ‘rules’ on the incoming information. It is suggested that the neural networks responsible for sleep and waking control are actively modulated by sensory inputs in order to enter and maintain normal sleep and wakefulness. Furthermore, both sensory stimulation and deprivation may induce changes in sleep/waking neural networks. This leads to the conclusion that the central nervous system and sensory input have reciprocal interactions, on which normal sleep/waking cycling and behaviour depends.

Under reporting of sleepiness and driving impairment in patients with sleep apnoea/hypopnoea syndrome.

Abstract: Under reporting of symptoms by patients with sleep apnoea/hypopnoea syndrome (SAHS) has been reported anecdotally, but investigation of the prevalence or determinants of this is limited. To assess this, repeated ratings in 99 patients with sleep apnoea/hypopnoea syndrome of pre-treatment Epworth sleepiness score, unintended napping, driving impairment and mood were obtained, first at presentation and then after treatment with continuous positive airway pressure (CPAP) therapy of median 22 (range 2-70) weeks duration. Median Epworth score for pre-treatment sleepiness rose from 12 (range 0-24) initially to 14 (range 5-24) retrospectively (P or = 11) Epworth score comprised 24% of all patients and 62% of initially 'normal' scorers. Unintended napping behaviour also was rated as significantly more severe on retrospective assessment (P 0.1). These results suggest a high prevalence of symptom minimization before treatment in patients with sleep apnoea/hypopnoea syndrome.

Perceived tiredness among adolescents and its association with sleep habits and use of psychoactive substances.

Abstract: This study investigated the variation in perceived tiredness among 11, 13 and 15-year-old Finnish adolescents (n = 4187). Additionally interrelationships between sleep habits, use of psychoactive substances (alcohol, tobacco and coffee) and perceived tiredness among 15-year-olds were examined. This study is part of an international, WHO-coordinated survey of school children's health and lifestyle (the HBSC Study). In Finland, research data represented the whole country. The data were collected in March-May 1994. Pupils responded anonymously to a standardized questionnaire during a class period. Subjective tiredness was very common and increased with age among adolescents. Perceived tiredness on at least four school mornings a week increased from 24 to 35% among boys and from 16 to 34% among girls. Feeling tired more often than once a week increased from 20 to 37% in girls and from 24 to 50% in boys. Structural equation models showed that interrelationships between three factors--sleep habits, use of psychoactive substances and perceived tiredness--were statistically significant. For these three factors the two remaining factors explained 24% of the variance of perceived tiredness among boys and 20% among girls, and the two remaining factors explained 42% (16%) of the variation in sleep habits. For the variance of the use of psychoactive substances sleep habits and perceived tiredness explained 26% (12%). Subjective tiredness is strongly age related; this together with the use of psychoactive substances and sleep habits regulate adolescents' daily life and well-being.

Endogenous and exogenous components in the circadian variation of core body temperature in humans

Abstract: Core body temperature is predominantly modulated by endogenous and exogenous components. In the present study we tested whether these two components can be reliably assessed in a protocol which lasts for only 120 h. In this so-called forced desynchrony protocol, 12 healthy male subjects (age 23.7 +/- 1.4 y) were subjected one by one to an artificial light/dark cycle of 20 h (10 lux vs. darkness). Core body temperature was measured continuously. The temperature data were analysed by an iterative method based on the assumption that the endogenous and exogenous components contribute to body temperature in an additive way. The results show that the average temperature curve is an almost perfect addition of the two components. The endogenous component differs from a sinusoid, and the relative contributions of the endogenous and exogenous components to the raw temperature curves differ substantially between the subjects. The average amount of unexplained variance in the individual data was 17%. Averaging of the body temperature curves over subjects reduced the unexplained variance to only 2%. This reduction in unexplained variance upon averaging over subjects must be due to the fact that most of the variance is either differently dependent on circadian phase for the various subjects or not dependent on circadian phase at all. The circadian pacemaker component revealed an average value of tau of 24.30 +/- 0.36 h, which is consistent with recent findings in the literature. We conclude that a short forced desynchrony protocol is sufficient for the distinction between the masking and pacemaker components of core body temperature. The same protocol can be used to study the influence of these components on all kinds of other physiological and psychological signals.

Microarousals in patients with sleep apnoea/hypopnoea syndrome

Abstract: Upper airway obstructions during sleep cause recurrent brief awakenings or microarousals. Standard criteria exist for sleep and respiratory event scoring, however, there are different definitions currently used to score microarousals. We therefore compared three definitions of microarousal (ranging from 1.5-3 s in duration) and one of awakening (>15 s). We examined their occurrence at the termination of apnoeas and hypopnoeas and their correlation with daytime sleepiness in patients with sleep apnoea/hypopnoea syndrome (SAHS). Sixty-three patients (aged 49, SD 10) had overnight polysomnography, multiple sleep latency tests (MSLT) and Epworth Sleepiness Scales (ESS). There were significantly more microarousals by any definition than there were awakenings (P<0.001) and there were more 1.5 s than 3 s microarousals (P<0.001). Significantly more apnoeas and hypopnoeas were terminated by 1.5 s microarousals (83% and 81%) than by 3 s microarousals (75%) (all P<0.001). Apnoea/ hypopnoea index (AHI) correlated significantly with objective daytime sleepiness (rho=-0.30, P<0.01). There were weakly significant relationships between all three microarousal definitions (-0.24

Poor sleep in adolescents: A study of 869 17-year-old Italian secondary school students

Abstract: Subjective sleep quality and its related factors were investigated in 869 (530 F, 339 M) 17-year-old adolescents, who were selected from the pupils of state-run secondary schools in the city of Pavia in the north west of Italy. The study was conducted cross sectionally, and it consisted of a questionnaire based survey. One hundred and forty-two subjects (16.5% of the whole sample, 19% of the females and 11.7% of the males) met the criteria chosen for definition as poor sleepers (namely, a complaint of «non restorative nocturnal sleep», «often» or «always» over the previous 12 mo). A significant association was found between chronic poor sleep and (1) gender (female) (2) emotional factors, such as worries, anxiety and depression (3) poor sleep hygiene (4) arousal related parasomnia. Only 4% of poor sleepers took sleep promoting drugs (including benzodiazepines, homeopathic products and other medications), generally without seeking medical advice.

Effect of nasal CPAP treatment on insulin sensitivity and plasma leptin

Abstract: There have been reports indicating that obstructive sleep and gave their consent. The protocol was approved by the Ethical Committee of the Tampere University Hospital. apnoea (OSA) may affect glucose metabolism (Brooks et al. 1994; Strohl et al. 1994) and insulin sensitivity (Tiihonen et al. All-night recordings were performed on eight subjects with an Alice 3⊂ digital polysomnograph (Healthdyne, Belgium) and 1993). However, two recent studies suggest that the relationship between glucose metabolism (Davies et al. 1994) or insulin on two subjects with a Static Charge Sensitive Bed (Biomatt⊂, Biorec, Finland). The sleep studies, adjusting the CPAP level resistance (Stoohs et al. 1996) and OSA is mediated through obesity. and compliance monitoring have been described earlier (Saarelainen et al. 1996). Resistance to insulin-stimulated glucose uptake is present in 25% of nonobese individuals with normal oral glucose After fasting for 12 h euglucaemic hyperinsulinaemic clamp (as described by Lahtela et al. 1985) was started at 07.00 hours tolerance, and in the majority of patients with non-insulin dependent diabetes. Insulin resistance is associated with using a constant intravenous insulin infusion of 40 mU/m/ min. Samples for plasma leptin (Human leptin RIA kit, Linco hyperinsulinemia, glucose intolerance, increased plasma triglyceride, decreased HDL-cholesterol and hypertension, all Research Inc., St. Charles, MO), cholesterol, HDL-cholesterol and triglyceride measurements were collected before the clamp. risk factors for coronary heart disease (Reaven 1988). We have performed an euglucaemic hyperinsulinaemic clamp The patients were instructed to keep their diet and physical activity constant until metabolic studies were repeated after on 10 nondiabetic patients referred to our sleep laboratory because of OSA. No control group was included. The patients 3 mo of nCPAP treatment. Table 1 gives the main characteristics of the group studied were randomly selected excluding all patients with other chronic diseases and current smokers. A detailed history and physical and the results before and after nCPAP treatment. Patients 1–6 used nCPAP 4.0–6.9 h per night (mean 5.6 h). Patient 7 examination were performed. It was confirmed that Hb, serum transaminases, glucose, creatinine and thyroxin were within had breaks in nCPAP treatment, but used it regularly during the week before control measurements. Patient 8 used a nCPAP normal limits. All patients were informed of the study protocol

Sleep deprivation increases somatostatin and growth hormone‐releasing hormone messenger RNA in the rat hypothalamus

Abstract: We studied the effect of sleep deprivation (SD) on the amount of somatostatin (SRIF) and growth hormone-releasing hormone (GHRH) mRNA in rat hypothalamic nuclei. According to earlier studies SRIF possibly facilitates REM sleep and GHRH slow-wave sleep. Adult male rats were sleep deprived by the gentle handling method either for 6 h during the first half of the light phase or for 12 h during the dark phase. Undisturbed rats sacrificed at the same time as the SD rats served as controls. After oligonucleotide in situ hybridization the amount of SRIF and GHRH mRNA was measured in brain sections by image analysis and cell count. SD increased the amount of SRIF mRNA in the arcuate nucleus (ARC). In the periventricular nucleus (PE) there was no effect. The amount of GHRH mRNA increased in the paraventricular nucleus (PA) in the 6 h SD group but no effect was detected in ARC. In the periventromedial hypothalamic area (pVMH) the amount of GHRH mRNA was higher in the control rats sacrificed in the morning (09.00 hours) than in the afternoon (15.00 hours), and SD had no effect. We conclude that SRIF cells in ARC and GHRH cells in PA are modulated by sleep loss, which is in accordance with the possible sleep regulatory function of these neuropeptides.

Event-related potentials to tones in the absence and presence of sleep spindles

Abstract: The present study focused on event-related potentials to tones in the presence and absence of sleep spindles. Six undergraduates were studied throughout an experimental night, following an adaptation session. The event-related potentials to tone stimuli were averaged for each subject. Separate averages were determined for trials on which no sleep spindle occurred 2 s before or after a tone and trials in which spindle activity was present. Both voltage distribution maps and multivariate analysis of the waveforms produced significant differences between these conditions, which could be seen as a higher initial positive component and sustained positively over the averaged epoch in the presence of spindles. Spectral analysis indicated that this result could not solely be ascribed to residual sigma activity in the spindle-present average. The results may provide insights into the functional role of sleep spindles in humans in addition to that suggested by a neurophysiological model of inhibition.

Respiratory patterns during sleep in Down's syndrome : importance of central apnoeas

Abstract: Obstructive sleep apnoea episodes have been reported repeatedly in Down's syndrome (DS) patients as a consequence of the presence of predisposing malformations or intercurrent pathology of the upper airways. There are no data on respiratory patterns of uncomplicated Down's syndrome subjects. In order to evaluate the eventual effects of central nervous system (CNS) impairment on respiration in DS, we studied the respiratory patterns during sleep of a group of 10 DS subjects, aged 8.6-32.2 y, without relevant upper airway pathology. In order to control the possible effects of sleep structure and mental retardation on the results obtained, we compared the findings in DS with those obtained from a group formed by subjects affected by fragile X syndrome (six males and one female, aged 10.0-15.42 y) another genetically determined type of mental retardation. Sleep structure was similar in both groups; however, DS subjects showed significantly higher indices of central sleep apnoea and of oxygen desaturation than fragile X patients (P < 0.005). As far as DS individuals were considered, a significant preponderance of central, as opposed to obstructive, sleep apnoeas was found (89.4% vs. 9.4%, respectively; 1.2% were mixed) which showed a significant age-related increase. Central respiratory pauses were mostly preceded by sighs, which occurred more frequently during sleep stages 1 and REM, and were often organized in long sequences of periodic-like breathing. During REM sleep, they were less frequently preceded by sighs and by body movements than during NREM sleep. Obstructive sleep apnoeas occurred more often during REM sleep and were more rarely preceded by sighs or by body movements. Both central and obstructive apnoeas induced significant oxygen desaturation in 50-69.6%. Sleep structure was not significantly modified by apnoeas and oxygen desaturation. We hypothesize that the increase in central sleep apnoeas is related to a dysfunction of the central respiratory control at a brainstem level in DS.

Sleepiness and driving: the experience of heavy goods vehicle drivers in the UK

Abstract: An interview survey of 996 heavy goods vehicle (HGV) drivers was undertaken. It was designed to investigate the relationship between HGV drivers' accidents, daytime sleepiness (measured using the Epworth Sleepiness Scale) and other relevant physical characteristics. The drivers were sampled randomly at motorway service areas. The average age was 41.4 y (SD 10.5), they drove an average of 69700 miles annually (SD 36120), and their average score on the Epworth daytime sleepiness scale was 5.65 (SD 3.31). They reported an average accident liability of 0.26 accidents in a 3-y recall period. Drivers who reported snoring regularly whilst sleeping at night or who were obese or who had a noticeably large collar size had higher accident liabilities than those not exhibiting these characteristics. Accident liability increased with increasing scores on the Epworth daytime sleepiness scale. These findings suggest that further investigation of the mechanisms behind the higher accident rates of some categories of HGV drivers would be justified in the interests of road safety.

Effect of intracerebroventricular administration of alpha-helical CRH (9-41) on the sleep/waking cycle in rats under normal conditions or after subjection to an acute stressful stimulus

Abstract: It has been shown in a previous study that specific lesioning of the noradrenergic system of the locus coeruleus abolished the sleep increase induced by immobilization stress. Given the fact that brain corticotropin-releasing hormone (CRH) acts as a neurotransmitter in the locus coeruleus under stress conditions, the present study was designed to investigate the involvement of CRH in the sleep increase seen after immobilization stress and on the spontaneous wake/sleep cycle. One hundred micrograms of the specific CRH receptor antagonist alpha-helical CRH (9-41), or vehicle alone was injected into the right lateral ventricle 30 min either before subjecting the animals to immobilization stress or before the spontaneous sleep-waking recordings onset. A single intracerebroventricular (i.c.v.) injection of alpha-helical CRH (9-41) had no effect on spontaneous paradoxical sleep but abolished the stress-induced increase, while wakefulness and slow-wave sleep were unchanged under both normal and stressful conditions. We therefore report that the involvement of endogenous CRH in the paradoxical sleep mechanism is dependent on the environmental conditions and suggest that, while the paradoxical sleep increase induced by immobilization stress may be mediated by endogenous corticotropin-releasing hormone, other mechanisms, either CRH-independent or situated at a distance from antagonist activity, may be involved in spontaneous paradoxical sleep. These results show, for the first time, that endogenous CRH may be involved in sleep-waking mechanisms only under stressful conditions and, in particular, as a fundamental component of the paradoxical sleep increase.

Reliability of scoring EMG orofacial events: polysomnography compared with ambulatory recordings

Abstract: The study of sleep bruxism is usually based on clinical history, signs and symptoms. The recording of electromyographic signals with either ambulatory portable home recorders or with polysomnographic techniques in the laboratory environment allows collection of objective data. The present study showed a 100% agreement with clinical evaluation in the recognition of bruxism episodes from the masseter electromyogram recorded with portable recorders and using the polysomnographic technique. On the contrary, scorers had difficulties in discriminating between different types of episodes (phasic, tonic and mixed), the between-scorers agreement varied between 62% and 63% and the kappa-values between 0.43 and 0.33. The ideal time base at which electromyographic signals should be integrated to allow for a good discrimination of bruxism patterns is 0.06 s. The results indicate that portable electromyography recorders are a valuable complement to polysomnographic recordings of orofacial motor activities as they provide a very good recognition rate with adequate time base data collection.

Correlates of sleep problems among men: The Vietnam Era Twin Registry

Abstract: The Vietnam Era Twin (VET) Registry includes 14,800 male twins born 1939-55 and in military service in 1964-75. A mailed health survey including the Jenkins Sleep Questionnaire was sent to 11,959 members and 8,870 (74.2%) provided responses on the frequency of sleep problems in the previous month. Prevalence of those experiencing conditions at least 1 day per month was 67.2% for waking often, 61.5% for waking tired/worn out, 48.1% for trouble falling asleep and 48.6% for awakening early. Ordinal logistic regression analysis was used to estimate sleep problems from demographic, behaviour and lifestyle characteristics, and morbid conditions. Black (vs. white) race, older age, church/religious group participation, social support, employment, cigarette smoking, light physical activity, and strenuous physical activity were associated with lower risk of one or more sleep problems. Eleven morbid conditions with a prevalence of 1% or more, coffee consumption, heavy alcohol consumption, and Framingham Type A behaviour pattern were associated with a higher risk of sleep problems. These analyses suggest that sleep problems may be one of the mechanisms relating reduced quality of life to many physical and behavioural characteristics. Fortunately, a number of the risk factors associated with sleep problems are lifestyle characteristics which, if modified, may reduce sleep problems.

Arousals and sleep stages in patients with obstructive sleep apnoea syndrome: Changes under nCPAP treatment.

Abstract: Nocturnal arousals are the essential cause of disturbed sleep structure in patients with obstructive sleep apnoea syndrome (OSAS). The aim of this study was to analyse the relationship between sleep stages, respiratory (type-R) and movement (type-M) related EEG arousals. Furthermore, the value of these arousals as a criterion for the efficiency of nCPAP treatment was estimated. We examined 38 male patients aged between 30 and 71 (49.1 +/- 20.9 SD) y. All patients suffered from OSAS. The mean respiratory disturbance index (RDI) was 47.3 +/- 27.8 per h. Polysomnographic monitoring was carried out on 4 subsequent nights: baseline night, 2 nights of nCPAP titration and nCPAP control night. Sleep was visually scored and EEG arousals were classified into type R and M, depending on whether changes of respiration or movement caused the arousal. The RDI, the R index (type-R/h), the M index (type-M/h) and the R and M indices in different sleep stages were calculated. During the baseline night a deficit of slow wave sleep (SWS) and REM sleep was found. Furthermore there were more type-R than type-M arousals registered (17.4 h-1 [3.6-43.6] vs. 5.9 h-1 [1.6-11.8]) (P < 0.01). They occurred during stages NREM 1, NREM 2 and REM (P < 0.01). An SWS sleep rebound and a reduction of the SWS and REM latencies were already found during the first CPAP night. The R index was reduced during the first CPAP night in all sleep stages (P < 0.01) and remained approximately the same in the following 2 nights (3. CPAP night: 1.1 h-1 [0.3-5.0]). Type M arousals occurred more in stages 1 and 2 (P < 0.01), and remained unchanged under nCPAP. We concluded that differentiation of nocturnal arousals may provide more detailed information regarding the influence of breathing disturbances on sleep. Respiratory related, not movement related, arousals may be a useful additional tool in judging the efficiency of OSAS.

Sleep during arousal episodes as a function of prior torpor duration in hibernating European ground squirrels

Abstract: EEG's were recorded in hibernating European ground squirrels during euthermic arousal episodes at an ambient temperature of 5.5 degrees C. Spontaneous torpor bouts ranged from 6 to 15 days, body temperature during torpor was 7.5 degrees C. The torpor duration prior to EEG measurements was experimentally manipulated: the animals were induced to arouse by gentle handling after torpor or less then 1 day (n = 3): 1-2 days (n=6), 3-4 days (n=9) and 5-12 days (n=9). The animals slept 71.5% of euthermic time, of which 61.4% NREM and 10.2%, REM sleep. NREM percentage was slightly positively and REM percentage negatively correlated with prior torpor duration (TD). Spectral analysis showed changes in EEG activity during the euthermic phase in the slow wave frequency range (1-4) and in higher frequencies. Prior TD specifically affected the slow waves, Slow wave activity decreased exponentially during the euthermic phase. The initial slow wave activity showed systematic increase with prior TD, which could be described by an exponentially saturating function, albeit with a relatively small time constant compared with spontaneous torpor duration. It is concluded that sleep during arousal episodes following torpor at an ambient temperature of 5.5 degrees C is affected both in structure and intensity by prior TD. The results are consistent with the proposition that torpor inhibits the restorative function of sleep.

Metamemory in narcolepsy

Abstract: People with narcolepsy consistently report diminished memory function attributable to the disorder, however, objective evaluations of memory performance in this clinical group remain inconclusive Previous evaluations of these subjective experiences have been primarily anecdotal with subjects required to provide global assessments of their memory function The present study aimed to evaluate subjective assessments of memory dysfunction more extensively comparing responses by narcoleptics, subjects experiencing excessive daytime sleepiness, and controls, on the Metamemory in Adulthood (MIA) questionnaire The results of the study indicate that subjects with narcolepsy have lower self efficacy for memory performance than either of the comparison groups, despite there being no significant difference between groups in relation to knowledge based aspects of memory functioning This lowered self efficacy in narcolepsy is expressed through increased anxiety about memory function, decreased evaluations of memory capacity and increased perceptions of memory decline in relation to the comparison groups It is argued that the negative cognitive self evaluations of narcoleptics potentially arise as a consequence of global psychosocial adjustment difficulties

Work hours, sleep patterns and fatigue among merchant marine personnel

Abstract: SUMMARY A field study of work and sleep patterns among commercial merchant marine personnel is reported Data collected over a 10-30-d period from 141 subjects aboard eight ships included information concerning work-rest schedules, sleep timing, alertness on the job and critical fatigue The data indicate that watchstanders on the 4-on, 8-off schedule show considerable disruption in their sleep The average sleep duration for all mariners is 66 h; watchstanders obtain their sleep in fragmented periods that are frequently less than 5 h in duration Analysis of critical fatigue shows an incidence of 1-24% across personnel and measures Of particular concern are the watchstanders on the 0400-0800 schedule, who sleep less than 4 h per 24-h period 22% of the time Potential countermeasures, including changes in scheduling and staffing are proposed