SLEEP

doi: 10.1093/sleep/22.1.5pmid: N/A

Feinberg, Irwin; Campbell, Ian G.; Benington, Joel H.; Heller, H. Craig; McCarley, Robert W.; Basheer, Radhika

doi: 10.1093/sleep/22.1.7pmid: 9989362

Rechtschaffen, Allan; Bergmann, Bernard M.; Gilliland, Marcia A.; Bauer, Kari

doi: 10.1093/sleep/22.1.11pmid: 9989363

SummaryTotal sleep deprivation (TSD) of rats for 24 hours or less by continually enforced locomotion has consistently produced subsequent rebounds of slow-wave or high-amplitude EEG activity in NREM sleep, which has contributed to the widely held view that this EEG activity reflects particularly “intense” or restorative sleep. These rebounds usually have been accompanied by substantial rebounds of REM sleep. In contrast, chronic TSD (2 weeks or longer) by the disk-over-water (DOW) method has produced only huge, long-lasting rebounds of REM sleep with no rebound of high-amplitude NREM sleep. To evaluate whether the different rebounds result from different methods or from different lengths of deprivation, rats were subjected to 24-hour TSD by the DOW method. Rebounds included increases in high-amplitude and slow-wave activity; ie, the methods produced similar rebound patterns following short-term TSD. (Chronic TSD by continually enforced locomotion would be strategically difficult and severely confounded with motor fatigue.) Rats subjected to DOW-TSD for 4 days, well before the development of severe TSD symptoms, showed primarily REM sleep rebounds. Rats subjected to 1 day of selective REM sleep deprivation, but not their closely yoked control rats, showed large, significant REM sleep rebounds, which evidently were not induced by the stress of the deprivation method per se. The combined findings prompted reexamination of published evidence relevant to “sleep intensity,” including “negative rebounds,” rebounds in other species, the effects of stress and fatigue, depth of sleep indicators, and extended sleep. The review points out pitfalls in the designation of any specific pattern as intense sleep.

Lancel, Marike

doi: 10.1093/sleep/22.1.33pmid: 9989364

SummaryThis paper reviews the sleep effects of systemically administered agonistic modulators of GABAA receptors, including barbiturates, benzodiazepines, zolpidem, zopiclone and neuroactive steroids, and the selective GABAA agonists muscimol and THIP. To assess the involvement of GABAA receptors in the physiologic regulation of sleep, the article emphasizes the hypnotic properties shared by agonistic modulators and by the selective agonists of the GABAA receptor complex. In both rats and normal sleeping individuals, agonistic modulators are able to reduce sleep latency, increase sleep continuity, and promote non-rapid-eye-movement (NREM) sleep as well as the occurrence of spindles. Furthermore, nearly all of these compounds have been shown to attenuate slow-wave activity (SWA) and to suppress the occurrence of REM sleep. In the same species, GABAA agonist(s) do not seem to affect sleep latency or REM sleep time, but may increase sleep continuity and NREM sleep and augment SWA while depressing spindle activity in humans. The distinct sleep effects of GABAA agonists may be due to their unspecific stimulation of GABAA receptors throughout the brain, and to the fact that they are poor substrates for uptake and probably exert more tonic effects than liberated GABA. If so, the involvement of GABAA receptors in the various aspects of sleep can be inferred more accurately from the hypnotic effects of agonistic modulators. This implies that an activation of GABAA receptors plays a crucial role in the initiation and maintenance of NREM sleep and in the generation of sleep spindles, but disrupts the processes underlying slow EEG components and the triggering of REM sleep.

Klerman, Elizabeth B.; Boulos, Ziad; Edgar, Dale M.; Mistlberger, Ralph E.; Moore-Ede, Martin C.

doi: 10.1093/sleep/22.1.45pmid: 9989365

SummaryA series of sleep deprivation (SD) experiments were performed to examine the relative influence of circadian and homeostatic factors on the timing of sleep in squirrel monkeys free-running in constant illumination. All SDs started at the beginning of subjective night and lasted 0, ¼, ½, 1, 1¼, or 1½ circadian cycles. These six lengths represented three pairs: (0,1), (¼, 1¼),(½, 1½). Within each pair, SD ended at the same circadian phase but differed by one circadian cycle in duration. Both before and after SD, consolidated sleep (CS) episodes occurred predominantly during subjective night, even after long SDs ending at the beginning of subjective day. CS duration was strongly influenced by circadian phase but had no overall correlation with prior wake duration. Sleep loss incurred during SDs longer than ¼ cycle was only partially recovered over the next two circadian cycles, though total sleep duration was closer to baseline levels after the second circadian cycle after SD. There was a trend toward a positive correlation between prior wake duration and the amount of NREM and delta activity measures during subjective day. Delta activity was not increased in the first 2 hours of CS after the SD. Relatively high levels of delta activity occurred immediately after the SD ended and again at the time of baseline CS onset. These data indicate that the amount of sleep and delta activity after SD in squirrel monkeys is weakly dependent on prior wake duration. Circadian factors appear to dominate homeostatic processes in determining the timing, duration and content of sleep in these diurnal primates.

Kraiczi, Holger; Hedner, Jan; Dahlöf, Pia; Ejnell, Hasse; Carlson, Jan

doi: 10.1093/sleep/22.1.61pmid: N/A

SummaryPharmacologic enhancement of serotonergic transmission by serotonin uptake inhibition has been suggested as one approach to improve upper-airway patency and thus nocturnal breathing in patients with obstructive sleep apnea (OSA). To test this hypothesis, we performed a double-blind, randomized, placebo-controlled crossover study testing the effect of paroxetine (20 mg od) on polysomnographic and psychopathologic outcomes in 20 male OSA patients (mean age 52.1 years, mean BMI 28.7 kg/m2, mean oxygen desaturation index on a previous screening 25.4/hour). The two treatment periods of 6 weeks and the separating washout period of 4 weeks were completed by 17 patients. Paroxetine reduced the apnea index during NREM sleep (−35%, p=0.003), but not during REM sleep. No significant effect on hypopnea indices was found. With the exception of a previously described REM-postponing effect (p=0.05), sleep architecture was not significantly influenced by paroxetine. Similarly, the effect of paroxetine on apnea was not associated with a significant overall alleviation of psychopathologic symptoms as rated on the Comprehensive Psychopathological Rating Scale or OSA-related daytime complaints assessed by visual analog scales. We conclude that enhanced serotonergic transmission improves breathing during NREM sleep in OSA. This effect is poorly related to effects on sleep architecture or daytime symptoms.

Sforza, Emilia; Krieger, Jean; Petiau, Christophe

doi: 10.1093/sleep/22.1.69pmid: N/A

SummaryIt has recently been described that the maximal respiratory effort developed at the end of an apnea (Pesmax)—which is regarded as an index of arousal threshold in patients with obstructive sleep apnea syndrome (OSA)—increases progressively during the night, probably as a consequence of associated sleep fragmentation. In order to find out whether the nocturnal trend of Pesmax may be more influenced by a sleep-dependent circadian rhythm than by sleep fragmentation, we revised the polygraphic recordings of 37 patients in whom obstructive apneas were recorded for at least 7 hours. In 15 of these patients, analysis was made for eight hours of the night. During each hour we analyzed at least 7 obstructive apneas, in which we measured the minimal esophageal pressure at the start of the apnea, the maximum value recorded at the end of the apnea (Pesmax), the difference from the minimum to the maximum (ΔPes), and the rate of increase in esophageal pressure (RPes). As indices of sleep fragmentation, we defined the number of arousals, awakenings and sleep state transitions. In the group of patients as a whole, we found a trend toward a gradual increase for apnea duration (F=98.8, p<0.001) and Pesmax F=31.6, p<0.001) which was significant from the first to the last hour. The time-dependent evolution of apnea duration and Pesmax showed that the rise in these two variables peaked during the first 3 hours of sleep, followed by a plateau and a decrease in the last hour of the night. This temporal profile was more evident when the analysis was available for 8 hours. No significant changes across the night were found for nocturnal hypoxemia and number of arousals. Considering the slope of Pesmax changes across the night, we saw that neither the apnea+hypopnea index nor the indices of sleep fragmentation affected the nocturnal trend. The present data demonstrate the presence of a nocturnal trend in arousal threshold in OSA patients independent of sleep fragmentation. The biphasic evolution of the arousal threshold may be caused by factors that influence the circadian and homeostatic processes.

Anic-Labat, Svetlana; Guilleminault, Christian; Kraemer, Helena C; Meehan, Jennifer; Arrigoni, Janis; Mignot, Emmanuel

doi: 10.1093/sleep/22.1.77pmid: N/A

SummaryOur goal was to validate a self-administered narcolepsy questionnaire focusing on cataplexy. Nine hundred and eighty three consecutive subjects entering the Stanford Sleep Disorder Clinic completed the questionnaire. Clinic physicians reported on the presence or absence of “clear-cut” cataplexy. Responses to 51 cataplexy-related questionnaire items were compared between subjects with clear-cut cataplexy (n=63) and all other patients (n=920). As previously reported, a large portion of the non-narcoleptic population was found to experience muscle weakness with various intense emotions (1.8% to 18.0%) or athletic activities (26.2% to 28.8%). Factor analysis and Receiver Operating Characteristic Curve (ROC) analysis were used to determine the most predictive items for clear-cut cataplexy. Most strikingly, cataplexy was best differentiated from other types of muscle weakness when triggered by only three typical situations: “when hearing and telling a joke,” “while laughing,” or “when angry.” Face or neck, rather than limbs, were also more specifically involved in clear-cut cataplexy. Other items, such as length of attacks, bilaterality, and alteration in consciousness, were poorly predictive. A simple decision tree was constructed to isolate high-(91.7%) and low-(0.6%) risk groups for cataplexy. This questionnaire will be used to increase diagnostic consistency across clinical centers, thus providing more homogenous subject pools for clinical and basic research studies.

Hublin, Christer; Kaprio, Jaakko; Partinen, Markku; Koskenvuo, Markku

doi: 10.1093/sleep/22.1.89pmid: 9989369

SummarySleep terrors are less frequent compared to other parasomnias, and there are no prevalence studies on adults. We performed a questionnaire study in a well-defined population-based sample, the Finnish Twin Cohort. The study population consisted of 11,220 subjects aged 33–60 years, responding to questions on the frequency of sleep terrors in childhood and as adults. In the first questionnaire about 9% reported sleep terrors often or sometimes in childhood, and 3.5% at least once monthly as adults. However, in a second more-detailed questionnaire, only 1% of those with at-least-monthly attacks in adulthood presented with features compatible with the minimal diagnostic criteria for sleep terrors of the International Classification of Sleep Disorders. There was also a strong correlation between current occurrence of nightmares and the report of sleep terrors. Although a clinically definable entity, sleep terrors seem to be unknown to lay people, at least in Finland. Therefore, the use of single items or brief question series on sleep terrors may give inaccurate results in questionnaires. An interview of a person who has witnessed the nocturnal attack suspected to be sleep terror is essential because of the patient's impaired recall of the episode. Our results also support the general view that sleep terrors are rare in adults.

Acebo, Christine; Sadeh, Avi; Seifer, Ronald; Tzischinsky, Orna; Wolfson, Amy R.; Hafer, Abigail; Carskadon, Mary A.

doi: 10.1093/sleep/22.1.95pmid: 9989370

AbstractStudy Objectives:This study provides estimates of reliability for aggregated values from 1 to 7 recording nights for five commonly used actigraphic measures of sleep patterns, reliability as a function of night type (weeknight or weekend night), and stability of measures over several months.Design and Setting:Data are from three studies that obtained 7 nights of actigraph data (using Mini Motionlogger actigraphs and associated validated algorithms [ASA]) on children and adolescents living at home on self-selected sleep-wake schedules.Participants:Participants were 169 children aged 12–60 months, and 55 adolescents aged 11–16 years.Measurements and Results:Up to 28% of weekly recordings may be unacceptable for analysis in young participants because of illness, technical problems, and participant noncompliance; studies aiming to collect 5 nights of actigraph data should record for at least 1 full week. Reliability estimates for values aggregated over any 5 nights were adequate (≥.70) for sleep start time, wake minutes, and sleep efficiency. Measures of sleep minutes and sleep period were less reliable and may require 7 or more nights for estimates of stable individual differences. Reliability for 1- or 2-night aggregates were poor for all measures. We found significant and high correlations between summer and fall session measures for all five variables when weekend nights were included.Conclusions:Five or more nights of usable recordings are required to obtain reliable actigraph measures of sleep for children and adolescents.