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The contribution of sleep to improvements in working memory scanning speed: a study of prolonged sleep restriction.

Working memory scanning and motor response speeds were assessed in chronically sleep restricted participants using the Sternberg item recognition paradigm (SIRP). Twenty-two healthy volunteers (ages 21-30) living in a controlled hospital environment were allowed either 4h of sleep opportunity (50% of habitual sleep) or 8h of sleep opportunity (100% of habitual sleep) for 12 days. Working memory scanning efficiency (time taken to access an item in working memory) was tested for the first 9 days of sleep restriction and improved over time in participants permitted an 8h sleep period, but did not change significantly in participants permitted a 4h sleep period. Speed of motor response (reaction time independent of cognitive processing) did not change significantly in either group. These results indicate that the efficiency of working memory scanning can improve with repeated practice given sufficient sleep, and that prolonged sleep restriction to 50% of habitual sleep prevents this improvement.

Adult↗

Effects of sleep deprivation and recovery sleep upon cell proliferation in adult rat dentate gyrus.

Numerous behavioral and environmental factors modulate the production of new cells in the adult mammalian brain. Although sleep loss has previously been shown to dramatically suppress brain cell proliferation, the effect of recovery sleep after a period of sleep deprivation is not known. Using the disk-over-water paradigm, adult male Sprague-Dawley rats were sleep deprived for 48 h. Separate groups were then allowed either an 8 h period of recovery sleep or an additional 8 h of sleep deprivation. A third group of rats served as a control, and were not sleep deprived. At 54 h, all rats received an injection of 5-bromo-2'-deoxyuridine (200 mg/kg, i.p.) and were killed 2 h later. When compared with control rats, a 36% reduction in cell proliferation was observed in the dentate gyrus of rats subjected to 56 h of sleep deprivation. A similar reduction in proliferation (39%) was observed in rats allowed an 8 h period of recovery sleep. In both deprivation groups, the magnitude of suppression of cell proliferation was approximately twice as large in the posterior hippocampus as it was in the anterior hippocampus. These data confirm previous results that an extended period of sleep deprivation exerts a strong suppressant effect on cell proliferation in the rat dentate gyrus, and demonstrate that this suppression of cell proliferation shows no evidence of recovery for at least 8 h following a 48 h period of sleep deprivation.

Analysis of Variance↗

Rapid eye movements density as a measure of sleep need: REM density decreases linearly with the reduction of prior sleep duration.

In the recovery nights from total and partial sleep deprivation there is a reduction of oculomotor activity during paradoxical sleep as compared to baseline nights. Aims of the present within-subjects study are to contribute in understanding the nature of the relationship between REM density and sleep need and to evaluate whether an inverse relationship exists between REM density and slow wave sleep (SWS) amount. Six healthy subjects were studied for 7 consecutive weeks with standard polysomnographic recordings. Variations in REM density were assessed in the recovery nights following a gradual sleep restriction, obtained by postponing the sleep onset time while maintaining the final awakening time constant. Results indicate that sleep curtailment decreases REM density in the ensuing recovery nights; the decrease is linearly related to the amount of sleep curtailment. The decrease in REM density parallels an increase in SWS, while no corresponding variation was found neither in the duration of paradoxical sleep nor in the latency of any other sleep stage. These results suggest that REM density could be used as a measure of sleep need.

Adult↗

Sleep latency measures of caffeine effects during sleep deprivation.

Studies of stimulants during sleep deprivation have used performance assessment batteries (PABs) and occasionally the multiple sleep latency test (MSLT) as measures. Another type of sleep latency test, the maintenance of wakefulness test (MWT), assesses ability to remain awake without assistance, rather than ability to go to sleep. The MWT previously has not been used in studies of stimulants during sleep deprivation. This study of caffeine during 64 h without sleep included a PAB, the MSLT, and a single MWT trial per day. The PAB and the MSLT were sensitive to caffeine effects during the first 24 h without sleep. The MWT demonstrated that caffeine improved ability to remain awake even after 2 nights of sleep deprivation. Ability to go to sleep and ability to stay awake during sleep deprivation appear to be affected differently by caffeine. PAB testing may fail to detect this stimulant effect because technicians prevent subjects from nodding off during PAB testing, an external support not available to subjects during the MWT and also not available in many real-world work environments. The MWT was more sensitive to stimulant amelioration of sleep-deprivation effects. The findings need to be validated with MWTs at other times of day and with other stimulants.

Adult↗

[Efficacy of uvulopalatopharyngoplasty (UPPP) and modifications in sleep structure in the sleep apnea syndrome (SAS)].

Thirty-four patients (32 male, 2 female; mean age 53 +/- 7 years) with confirmed sleep apnea syndrome (SAS) were studied before and after uvulopalatopharyngoplasty (UPPP). Clinical symptoms were tiredness, excessive daytime sleepiness and snoring. All patients were overweight. Patients underwent a thorough physical and oropharyngeal examination and polysomnography before and 3 months after surgery. On the basis of post-operative results, patients are divided into 3 groups: --group 1: 16 cured patients: apnea index (A.I./h) 38 +/- 17 before and 4.4 +/- 4 apneas/h sleep after surgery. Improved nocturnal hypoxemia: mean minimum oxyhemoglobin saturation (SAO2) before and after UPPP in NREM sleep 83 +/- 4% v. 90 +/- 4% in REM sleep 76 +/- 11% v. 85 +/- 7%. Uninterrupted sleep is restored; --group 2: 8 improved patients: A.I./h of 64 +/- 11 before and 20 +/- 6 after UPPP: improved nocturnal hypoxemia: mean minimum SAO2 in NREM sleep 74 +/- 10% before and 86 +/- 6% after UPPP: in REM sleep 59 +/- 9% before and 79 +/- 6% after UPPP, lower amount and percentage of fragmented sleep; --group 3: 10 non-improved patients: A.I./h unchanged 55 +/- 22% before and 50 +/- 20% after UPPP. Persistent nocturnal hypoxemia: mean minimum SAO2 in NREM sleep 76 +/- 13 before and 81 +/- 12% after UPPP: in REM sleep 63 +/- 16% before and 65 +/- 24% after UPPP. Sleep remains fragmented. In this last group patients are more overweight and all suffer from severe SAS with greater nocturnal oxyhemoglobin desaturation. Surgical treatment by UPPP is shown to be effective for 70% of our patients. Better results are obtained when SAS is less severe and overweight less important.

Adult↗

Sleep complaints are not corroborated by objective sleep measures in post-traumatic stress disorder: a 1-year prospective study in survivors of motor vehicle crashes.

Disturbed sleep is a common complaint among patients with post-traumatic stress disorder (PTSD). However, laboratory studies of sleep in PTSD have provided inconsistent evidence of objective sleep disturbances. A major shortcoming of most previous studies is the fact that they were performed retrospectively in patients with chronic PTSD, often complicated by comorbid psychiatric disorders and drug abuse. Thus, little is known about the development of sleep disturbances in recently traumatized subjects. In this study, 102 motor vehicle collision (MVC) survivors were followed from the time of collision throughout 1 year. Nineteen subjects hospitalized for elective surgery served as a comparison group. Subjective quality of sleep was assessed using the mini-Sleep Questionnaire and the Sleep Habit Questionnaire. In addition, a 48-h actigraphic recording was obtained 1 week, 3 and 12 months after the collision. At 12 months, a structured clinical interview (SCID) was administered to reach a formal diagnosis of PTSD. Twenty-six of the MVC survivors, but none of the comparison subjects, met the diagnostic criteria for PTSD. While MVC survivors with PTSD reported markedly poorer sleep as reflected by significantly higher scores on the mini-Sleep Questionnaire, there were no significant differences between the three groups on the actigraphic measures that were largely normal. These results, which were obtained in subjects with no evidence of active psychiatric symptoms at the time of trauma and free of psychotropic or hypnotic medications, further support previous polysomnographic (PSG) studies suggesting that altered sleep perception, rather than sleep disturbance per se, may be the key problem in PTSD.

Accidents, Traffic↗

Physician education in sleep and sleep disorders: a national survey of U.S. medical schools.

A national survey was conducted of 126 accredited medical schools in the United States to evaluate physician education in sleep and sleep disorders and to identify potential obstacles to effective teaching in the area. Parallel survey instruments were designed to evaluate preclinical and clinical training in sleep. Instructors indicated the specific courses in which this material is taught, the format of teaching, methods of student evaluation, assigned readings and clinical experience and educational resources provided. A total of 545 responses were received, which represents an 82.6% overall response rate. Responses were obtained from all accredited medical schools, and the sample was about equally divided between preclinical and clinical course directors. Less than 2 hours of total teaching time is allocated to sleep and sleep disorders, on average, with 37 schools reporting no structured teaching time whatever in this area. Only 8% of medical students are trained in the use of sleep laboratory procedures, and 11% have participated in the clinical evaluation of sleep-disordered patients. Less than 5% of medical schools offer 4 or more hours of didactic teaching on sleep, most of which consists of 4th year elective experiences. More than two-thirds of the survey respondents stated that current education is inadequate and that additional time should be devoted to this area. The major obstacles reported are the unavailability of qualified faculty, lack of curriculum time and the need for additional clinical and educational resources. Overall, it appears that physician education in sleep and sleep disorders is largely inadequate, despite increasing evidence of the role of sleep in patient health and well-being.

Adult↗

Nefazodone and REM sleep: how do antidepressant drugs decrease REM sleep?

In previous uncontrolled studies, nefazodone, a new antidepressant drug, increased REM sleep or had no effect on REM sleep. We report a double-blind, placebo-controlled, parallel group study on effects of nefazodone (N) on polysomnographic sleep variables in healthy human volunteers. Nefazodone was administered for 16 consecutive days, and nocturnal sleep, as well as multiple sleep latency test (MSLT), was monitored before, during, and after N administration. We found that N had no effect on any measured REM sleep variable including REM sleep duration, REM density, and nocturnal REM sleep distribution. Nefazodone also had no significant effect on nocturnal total sleep time or NREM variables, but increased daytime alertness measured by the MSLT. Since N is a potent serotonin reuptake blocker, the present findings that N had no effect on REM sleep cast doubt on the hypothesis that antidepressant drugs decrease REM sleep by increasing serotonergic neurotransmission. A review of other relevant work also casts doubt on this hypothesis.

Adolescent↗

Presentation and reading level of sleep brochures: are they appropriate for sleep disorders patients?

OBJECTIVE: Sleep-disorders patients must be given information and health education they understand. The purpose of this study was twofold: (1) to assess suitability of American Sleep Disorders Association and National Sleep Foundation patient education brochures; and (2) to assess one widely used brochure, using patient input and patient literacy level, as a model for development of future materials. DESIGN: Twelve American Sleep Disorders Association and National Sleep Foundation brochures were assessed for reading level using Grammatik, and for design, presentation, and motivating qualities using the Suitability Assessment of Materials (SAM). Patient literacy level was assessed using the Rapid Estimate Of Adult Literacy in Medicine (REALM). SETTING: The Louisiana State University Medical Center sleep clinic, faculty private sleep clinic, and in the sleep center laboratory. PATIENTS OR PARTICIPANTS: During the months of February-May 1997, 170 sleep disorders patients, 39% African American, 59% white participated in the study. Participants ranged in age from 18-73 years, with a mean age of 46. MEASUREMENTS AND RESULTS: Suitability scores for the 12 brochures indicate that none scored in the superior range, 83% scored adequate, and 17% scored not suitable. Ninety-four percent of the brochures were written on a 12th grade level or higher, yet 37% of the sleep patients tested were reading at less than a 9th grade level. Low-level readers were significantly more likely than their higher-reading-level counterparts to report that a brochure was too long (22% vs 12%; p < .05), and that they would need help reading it (44% vs 3%; p < .001). CONCLUSIONS: Patients need sleep information given to them on a level they understand. When developing and selecting appropriate materials, reading level, length, and suitability of written material should be considered.

Adolescent↗

Sleep deprivation and its effect on an index of cardiac parasympathetic activity in early nonREM sleep in normal and epileptic subjects.

The effect of 24-hour sleep deprivation on cardiac vagal tone during the first 90 minutes of sleep was studied in 16 subjects using a new real-time index of cardiac parasympathetic activity. The level of cardiac vagal tone in subjects who were sleep deprived was more than doubled that in non-sleep-deprived subjects during sleep stage 0 immediately prior to the onset of sleep stage 1. The mean cardiac vagal tone fell significantly (p < 0.01), from a high level of 19.2 arbitrary units of a linear vagal scale (LVS) to 10 units on reaching slow-wave sleep stage 4 in sleep-deprived epileptic subjects, There was a similar fall in cardiac vagal tone from 18.7 units to 12 units in the LVS in sleep-deprived normal subjects, but this was not statistically significant. There was no change in the mean vagal tone of non-sleep-deprived normal subjects. We propose that the cardiac vagal tone can be used as an objective index of sleep propensity.

Adult↗

Effect of continuous positive airway pressure versus supplemental oxygen on sleep quality in obstructive sleep apnea: a placebo-CPAP-controlled study.

STUDY OBJECTIVE: We investigated the short-term effectiveness of continuous positive airway pressure (CPAP) and oxygen in improving sleep quality in patients with obstructive sleep apnea (OSA). DESIGN: Randomized, double-blind, placebo-controlled, parallel study. SETTING: General Clinical Research Center at a university hospital. PATIENTS: Seventy-six patients with untreated OSA. INTERVENTIONS: Patients were randomly assigned to 1 of 3 treatments (CPAP, placebo-CPAP, or nocturnal oxygen at 3 L per minute) for 2 weeks. Sleep quality was assessed at baseline and after 1 and 14 days of therapy. Repeated-measures analysis of variance was used to evaluate treatment and time effects, and their interaction. MEASUREMENTS AND RESULTS: Sixty-three patients completed the protocol. When compared with placebo-CPAP and nocturnal oxygen, CPAP increased rapid eye movement (REM) sleep and significantly reduced stage 1 sleep and the number of stage shifts (p < or = .003). CPAP improved, to within normal limits, the apnea-hypopnea index, total arousal index, and mean oxyhemoglobin saturation (p < or = .001). The effects of CPAP were apparent during the first night of therapy. Oxygen improved only mean nocturnal saturation (p = .009). CPAP had no significant effect on stage 2 sleep or slow-wave sleep. CONCLUSIONS: CPAP was associated with an improvement in sleep quality in patients with OSA by consolidating sleep, reducing stage 1 sleep, and improving REM sleep. CPAP was effective in correcting the respiratory and arousal abnormalities of OSA. The effectiveness of supplemental oxygen was limited to oxyhemoglobin desaturation.

Arousal↗

Testosterone replacement in hypogonadal men: effects on obstructive sleep apnoea, respiratory drives, and sleep.

The obstructive sleep apnoea syndrome occurs predominantly in men. To determine the effect of testosterone on ventilatory function and whether testosterone may play a role in the development of obstructive apnoea, we performed waking ventilatory drive studies and sleep studies in five hypogonadal men. These androgen-deficient subjects were studied both while receiving no treatment and after six weeks of testosterone replacement therapy (testosterone oenanthate 200 mg i.m. every 2 weeks). Hypoxic ventilatory drive decreased significantly, from 158 +/- 39 (mean +/- SEM) off testosterone to 88 +/- 19 on testosterone therapy (P less than 0.05). Hypercapnoeic ventilatory drive did not change significantly on testosterone. Obstructive sleep apnoea developed in one man and markedly worsened in another man in association with testosterone administration. Both of these subjects also exhibited marked decreases in oxygen saturation with the development of cardiac dysrhythmias during sleep and large increases in haematocrit. The remaining three hypogonadal men did not demonstrate significant sleep apnoea either on or off testosterone. The percentage of sleep time spent in REM sleep increased from 14 +/- 3% to 22 +/- 2% when the men were receiving testosterone (P less than 0.01), but the episodes of sleep apnoea tended to occur during non-REM sleep. We conclude that in some hypogonadal men, replacement dosages of testosterone may affect ventilatory drives and induce or worsen obstructive sleep apnoea. The obstructive sleep apnoea syndrome is a potential complication of testosterone therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Altered circadian melatonin secretion patterns in relation to sleep in patients with chronic sleep-wake rhythm disorders.

Human well-being depends on the entrainment of endogenous circadian rhythms of biological functions and the sleep-wake rhythm. Although the incidence of otherwise healthy subjects with chronically altered sleep-wake rhythms is rather low, the investigation of these patients provides new sights into circadian entrainment mechanisms. We therefore examined the circadian rhythm of circulating melatonin and the sleep-wake rhythm in five patients with chronic sleep-wake rhythm disorders and ten age-matched healthy controls. All patients showed altered circadian melatonin rhythm parameters in relation to their sleep-wake cycle compared to age-matched controls. These alterations were random, i.e., independent of the type, the duration, and the age of onset of the disorder. The melatonin onset to sleep onset interval varied between the patients and the melatonin acrophase to sleep offset interval was prolonged in four patients. These findings indicate individual phase relations between the circadian melatonin rhythm and the sleep-wake cycle in patients with chronic sleep-wake rhythm disorders. Since the prolonged melatonin acrophase to sleep offset interval was the most consistent finding independent of aetiological origins, this abnormality may be one possible maintaining factor in chronic sleep-wake rhythm disorders due to reduced phase-resetting properties of the circadian pacemaker. Furthermore, rather low circadian melatonin amplitudes and a subsensitivity to daylight may maintain the disorder in at least some patients.

Adult↗

Sleep and arousal, synchrony and independence, among mothers and infants sleeping apart and together (same bed): an experiment in evolutionary medicine.

Although solitary sleeping in infancy is a very recent custom, limited to Western industrialized societies, and most contemporary people practice parent-infant co-sleeping, virtually all laboratory research on sleep in human infants assumes that solitary infant sleep is the normal and desirable environment. We have used evolutionary and developmental data to challenge this view. We suggest that co-sleeping provides a sensory-rich environment which is the more appropriate environment in which to study infant sleep. In addition, two preliminary, in-laboratory, polygraphic investigations of mother-infant co-sleeping are reported in normal infants, within the peak age range for sudden infant death syndrome (SIDS). Five mother-infant pairs co-slept one night in the first study; in the second, three additional pairs slept separately for two nights and co-slept the third consecutive night. The results suggest that co-sleeping is associated with enhanced infant arousals and striking temporal overlap (synchronicity) in infant and maternal arousals, and that, possibly as a result, co-sleeping mothers and infants spend more time in the same sleep stage or awake condition. The implications of the hypothesis and preliminary results for research on the normal development of infant sleep and on SIDS are discussed.

Female↗

Elementary students' sleep habits and teacher observations of sleep-related problems.

Sleep affects the health and well-being of children and plays a key role in preventing disease and injury, stability of mood, and ability to learn. Unfortunately, children often do not get adequate sleep on a regular basis. This study surveyed 199 fifth-grade students regarding their sleep habits using the Sleep Self-Report (SSR) instrument (child's form), the Morningness/Eveningness (M/E) Scale, and additional demographic questions. Students' teachers also were asked to evaluate their students' behavior using the Teacher's Daytime Sleepiness Questionnaire (TDSQ). Results indicated many students experienced problems with sleep-related behavior. However, correlating the TDSQ scale with the SSR Daytime Sleepiness Subscale produced a weak correlation coefficient, indicating teachers may not be able to accurately identify students with sleep problems. Overall findings indicated these students displayed sleep behavior similar to other US children. However, research involving children's sleep behavior is limited, and more research is needed. Parents should monitor their children's sleep times, and teachers need to be aware how sleep deprivation can affect children's mood, reaction time, and concentration. Health education curricula need to include sleep-related instruction at all grade levels to address this concern.

Child↗

Effect of sleep and sleep deprivation on ventilatory response to bronchoconstriction.

To characterize ventilatory responses to bronchoconstriction during sleep and to assess the effect of prior sleep deprivation on ventilatory and arousal responses to bronchoconstriction, bronchoconstriction was induced in eight asthmatic subjects while they were awake, during normal sleep, and during sleep after a 36-h period of sleep deprivation. Each subject was bronchoconstricted with increasing concentrations of aerosolized methacholine while ventilatory patterns and lower airway resistance (Rla) were continually monitored. The asthmatic patients maintained their minute ventilation as Rla increased under all conditions, demonstrating a stable tidal volume with a mild increase in respiratory frequency. Inspiratory drive, as measured by occlusion pressure (P0.1), increased progressively and significantly as Rla increased under all conditions (slopes of P0.1 vs. Rla = 0.249, 0.112, and 0.154 for awake, normal sleep, and sleep after sleep deprivation, respectively, P less than 0.0006). Chemostimuli did not appear to contribute significantly to the observed increases in P0.1. Prior sleep deprivation had no effect on ventilatory and P0.1 responses to bronchoconstriction but did significantly raise the arousal threshold to induced bronchoconstriction. We conclude that ventilatory responses to bronchoconstriction, unlike extrinsic loading, are not imparied by the presence of sleep, nor are they chemically mediated. However, prior sleep deprivation does increase the subsequent arousal threshold.

Adult↗

Sleep patterns and sleep-related complaints of Brazilian interstate bus drivers.

Sleep-related complaints have become a highlight for physicians as well as public health administrators. Studies of sleep patterns and sleep-related complaints of shift workers have been useful in minimizing reduction in the quality of life due to the warping of the sleep-wake cycle. The objective of the present study was to assess patterns of sleep, sleep-related complaints as well as physical activity and scoring rates for depression and anxiety in interstate bus drivers. Data were obtained with a sleep questionnaire, with the Beck inventory for depression, and the State-Trait Anxiety Inventory (STAI). A total of 400 interstate bus drivers from the northern, southern, central-western and south-eastern regions of Brazil were interviewed. Sixty percent of the subjects interviewed presented at least one sleep-related complaint, 16% admitted to have dozed at the wheel while on duty, and 41% stated that they exercised on a regular basis. Other sleep disturbance complaints reported were: sleep latency 29'17"; physical fatigue, 59.8%; mental fatigue, 45.4%; sleepiness, 25.8%; irritability, 20.6%; insomnia, 37.5%, respiratory disturbances, 19. 25% and snoring, 20.75%. Scores for anxiety and depression were not in the pathological range. The present data reinforce the view that bus drivers are generally discontent with shift work and its effects on sleep. Consequently, it is very important to establish an appropriate work schedule for drivers, besides implementing photo-therapy and physical activities in order to minimize sleepiness when driving.

Anxiety↗

'Sleep attacks' or 'unintended sleep episodes' occur with dopamine agonists: is this a class effect?

Controversial reports of sudden onset 'sleep attacks' resulting in road traffic accidents have recently been reported in patients with Parkinson's disease (PD) taking the non-ergot dopamine D(2 )/D(3) receptor agonists pramipexole and ropinirole. These reports have generated considerable debate as the concept of 'sleep attacks' is disputed amongst sleep specialists and most believe that isolated 'sleep attacks' not preceded by warning on the background of chronic sleepiness or 'unintended sleepiness' do not exist. A series of case reports suggested that this phenomenon may not be exclusive to the non-ergot dopamine agonists such as pramipexole or ropinirole and indeed may occur with most dopaminergic agents. Recent evidence suggest that a 'sleepiness' or 'hypoactivity' reaction to dopaminergic therapy may be related to underlying dopamine deficiency of PD rather than a drug effect. In this report we provide the evidence for the phenomenon being a class effect attributable to all dopamine agonists currently employed in the management of PD. Controversy surrounding excessive daytime sleepiness (EDS) in PD and the use of the Epworth Sleepiness Scale (ESS) in relation to PD is also discussed. In spite of variable reports, EDS is recognised to be common in PD and is likely to be related to both the disease process and drug therapy. Studies using multiple sleep latency tests have also reported differing results in PD although a recent study indicated that a subset of 'sleepy' patients with PD may experience pathological somnolence with resultant detrimental consequence on daytime and cognitive functions. We recommend that the issue of 'sleepiness' or 'sleep attacks' in PD should be routinely checked in all patients with PD and indirectly assessed by using either the ESS or the recently introduced Parkinson's Disease Sleep Scale. Those with reported 'sleep attacks' or 'unintended sleep episodes' and excessive daytime sleepiness while taking dopamine agonists or dopaminergic agents such as levodopa should have a review of their medication, should not be driving a car on their own and some may merit formal sleep architecture studies. The latter may identify sleep disorders such as secondary narcolepsy which may benefit from the use of a wakefulness promoting agent.

Disorders of Excessive Somnolence↗