Showing papers in "Sleep in 1992"

Reliability and factor analysis of the Epworth Sleepiness Scale.

Abstract: The Epworth Sleepiness Scale (ESS) is a self-administered eight-item questionnaire that has been proposed as a simple method for measuring daytime sleepiness in adults. This investigation was concerned with the reliability and internal consistency of the ESS. When 87 healthy medical students were tested and retested 5 months later, their paired ESS scores did not change significantly and were highly correlated (r = 0.82). By contrast, ESS scores that were initially high in 54 patients suffering from obstructive sleep apnea syndrome returned to more normal levels, as expected, after 3-9 months' treatment with nasal continuous positive airway pressure. The questionnaire had a high level of internal consistency as measured by Cronbach's alpha (0.88). Factor analysis of item scores showed that the ESS had only one factor for 104 medical students and for 150 patients with various sleep disorders. The ESS is a simple and reliable method for measuring persistent daytime sleepiness in adults.

Automatic sleep/wake identification from wrist activity

Abstract: The purpose of this study was to develop and validate automatic scoring methods to distinguish sleep from wakefulness based on wrist activity. Forty-one subjects (18 normals and 23 with sleep or psychiatric disorders) wore a wrist actigraph during overnight polysomnography. In a randomly selected subsample of 20 subjects, candidate sleep/wake prediction algorithms were iteratively optimized against standard sleep/wake scores. The optimal algorithms obtained for various data collection epoch lengths were then prospectively tested on the remaining 21 subjects. The final algorithms correctly distinguished sleep from wakefulness approximately 88% of the time. Actigraphic sleep percentage and sleep latency estimates correlated 0.82 and 0.90, respectively, with corresponding parameters scored from the polysomnogram (p < 0.0001). Automatic scoring of wrist activity provides valuable information about sleep and wakefulness that could be useful in both clinical and research applications.

Self-reported sleep disturbances in employed women.

Abstract: To explore the incidence and types of sleep disturbances in employed women, 760 registered nurses completed a health survey that included questions about their sleep patterns and sleep quality. Comparisons are made between those nurses working permanent day, permanent evening, permanent night, and rotating shifts. As expected, there were higher incidences of sleep disturbances and excessive sleepiness for women working night and rotating shifts, but age and family factors, rather than caffeine and alcohol intake, contributed to the differences in types of sleep disturbances these women experienced.

Wrist actigraphy in insomnia

Abstract: To assess the use of actigraphy in evaluating insomnia, 36 patients with a serious complaint of insomnia slept 3 nights each in the laboratory, where the usual polysomnograms (PSGs) were obtained as well as actigraphic assessments of their sleep. Patients also wore actigraphs for 7 days at home, were extensively interviewed and filled out psychometric tests. Based on all this information, the patients were then diagnosed according to the International Classification of Sleep Disorders. Averaged over the 3 nights for each insomniac, the mean discrepancy between actigram and PSG was 49 minutes per night. In three-fourths of the cases, actigram and PSG agreed to within 1 hour on the total amount of sleep per night. Discrepancies, however, were not random: In patients with psychophysiologic insomnia and in insomnia associated with psychiatric disease, the actigram typically overestimated sleep when compared with the PSG. In patients with sleep-state misperception, the actigram was either quite accurate or it underestimated sleep when compared with the PSG. Comparing laboratory with home sleep, one-third of all insomniacs slept better in the laboratory and two-thirds slept better at home. In addition, night-by-night variability was higher at home than in the laboratory. Based on our study, we now recommend actigraphy as an additional tool in the clinical evaluation of insomnia, but we believe that in complex cases it should be combined with 1 PSG night in the sleep disorders center.

Sleep and cardiorespiratory characteristics of infant victims of sudden death: a prospective case-control study.

Abstract: We studied the polygraphic sleep recordings of 30 infants who eventually died of sudden infant death syndrome (SIDS) and those of 60 matched control infants. All records were extracted from 20,750 sleep studies collected prospectively in 10 sleep laboratories. Of the 30 future SIDS victims, 5 were siblings of SIDS victims and 9 were studied after an apparent life-threatening event. For each SIDS victim, two normal control infants were matched for sex, gestational age, postnatal age and weight at birth. The future SIDS infants were reported to have more frequent episodes of regurgitations after feeding (p = 0.01) and profuse sweating during sleep (p = 0.01) than the control subjects. Only two polysomnographic variables characterized the future SIDS infants. Compared to control subjects, the SIDS infants moved less during sleep (p = 0.04) and had significantly more frequent obstructed breathing events. Obstructive and mixed apneas were seen in 23 of 30 future SIDS victims, but in only 9 of 60 control subjects (p = 0.01). The obstructed and mixed apneas lasted longer in the SIDS than in the control infants (p = 0.01) but did not exceed 15 seconds. The obstructed breaths occurred mainly in rapid eye movement sleep (78% of the events) and were accompanied by drops in heart rates to 68 beats per minute and in SaO2 levels to 75%. The present report adds further indirect evidence for a possible sleep-related impairment of respiratory control in some infants who eventually died of SIDS.

Prominent eye movements during NREM sleep and REM sleep behavior disorder associated with fluoxetine treatment of depression and obsessive-compulsive disorder

Abstract: The clinical polysomnographic (PSG) reports of 2,650 consecutive adults studied during 41 months were reviewed retrospectively to identify all patients treated with fluoxetine or tricyclic antidepressants. The PSG reports of four other adult groups were also reviewed: periodic limb movement (PLM) disorder (n = 28); sleep terror/sleepwalking (ST/SW) (n = 54); rapid eye movement (REM) sleep behavior disorder (RBD) (n = 70); patients with clinically unremarkable sleep during two consecutive PSG studies (n = 30). Standard PSG recording and scoring methods were employed. A total of 1.5% (n = 41) and 2.0% (n = 52) of patients were receiving fluoxetine or tricyclics (amitriptyline or nortriptyline, n = 31; imipramine or desipramine, n = 16; protriptyline or trimipramine, n = 5). A selective association between fluoxetine and extensive, prominent eye movements in nonrapid eye movement (NREM) sleep was detected, utilizing Fisher's exact one-tailed statistic (p less than 0.00001 for each comparison). The detection rates were fluoxetine, 48.8% (20/41); tricyclics, 5.8% (3/52); RBD, 4.3% (3/70); objectively normal sleepers, 3.3% (1/30); PLM, ST/SW, 0% (0/82). These groups had similar mean ages (31.5-45.4 years) and gender distributions (50.0-60.7% male), apart from RBD. The effect of fluoxetine, a potent and specific serotonin reuptake inhibitor, on NREM eye movements is postulated to derive from potentiation of serotonergic neurons that inhibit brainstem "omnipause neurons", which, in turn, inhibit saccadic eye movements, thus resulting in disinhibited release of saccades. In addition, a 31-year-old man with obsessive-compulsive disorder developed RBD soon after starting fluoxetine therapy, which persisted at PSG study 19 months after fluoxetine discontinuation.

Caffeine use as a model of acute and chronic insomnia

Abstract: It was hypothesized that the metabolic effects of caffeine, which can be objectively measured (i.e. physiological, "arousal"), could be used to develop a physiological arousal model of chronic insomnia in a group of normal young adults. Twelve normal young adult males participated for 11 nights after laboratory adaptation. Subjects received 400 mg of caffeine three times a day for 7 nights and days. As predicted, the use of caffeine resulted in increased metabolic rate. Sleep efficiency was significantly reduced by caffeine and multiple sleep latency tests (MSLTs) were significantly increased. Some adaptation to the metabolic, sleep efficiency, and MSLT effects of caffeine was seen over the week of administration. Withdrawal effects (i.e. rebound sleep or sleepiness) were not seen for metabolic, MSLT or sleep variables. The data indicated that caffeine was effective in producing significant metabolic and sleep effects and that those effects were related. The results were consistent with the interpretation that a chronic decrease in sleep efficiency associated with increased physiological arousal, although producing subjective dysphoria, does not produce a physiological sleep debt.

Sleep in normal late pregnancy.

Abstract: Twelve women in their third trimester of pregnancy and 10 age-matched nonpregnant controls underwent complete polysomnography for one night in the laboratory. Seven of the original women returned for a second study 3-5 months postpartum. During late pregnancy, women showed increased wake after sleep onset (WASO) and a lower sleep efficiency in comparison with the control group. The percentage of rapid eye movement (REM) sleep was significantly decreased and the percentage of stage 1 significantly increased compared to the nonpregnant group. At 3-5 months postpartum, a significant reduction in WASO and increased sleep efficiency were noted. However, only a slight increase was noted in REM sleep during the postpartum period compared to the prepartum period. The most frequent sleep complaints in the pregnant group were restless sleep, low back pain, leg cramps and frightening dreams. In summary, in accordance with their complaints, women in their third trimester demonstrated polysomnographic patterns of sleep maintenance insomnia.

Patients' acceptance of psychological and pharmacological therapies for insomnia.

Abstract: This study evaluated the acceptance of psychological and pharmacological therapies among chronic insomniacs and noncomplaining good sleepers. After reading a brief written description of two treatment methods commonly used for persistent insomnia (i.e. cognitive-behavior therapy and pharmacotherapy), the subjects rated in a counter-balanced order several dimensions of these two treatment modalities. The results showed that the psychological intervention was rated as more acceptable and more suitable than the pharmacological one among both insomniacs and their noncomplaining significant others. Behavior therapy was also expected to be more effective on a long-term basis and to produce fewer side effects as well as more benefits on daytime functioning. The clinical implications and relevance of treatment acceptance in the management of insomnia are discussed.

Long-term compliance with nasal continuous positive airway pressure (cpap)in obstructive sleep apnea patients and nonapneic snorers

Abstract: In a prospective study aimed at evaluating objectively the compliance with nasal continuous positive airway pressure (CPAP) treatment, 233 obstructive sleep apnea (OSA) (apnea index, > 10 apneas/hour) patients and 36 nonapneic snorers were studied. The compliance to treatment was measured by the mean rate of use of the CPAP device, obtained from a built-in time counter. The follow-up period was 874 +/- 48 in OSA patients and 675 +/- 83 in snorers. CPAP was proposed to all OSA patients but only to those snorers who felt improved after an initial laboratory night on CPAP. Nineteen OSA patients refused CPAP. Of the 214 OSA patients who accepted CPAP, 181 are still on treatment, with a mean daily rate of use of 5.6 +/- 0.1 hours (mean +/- SEM); 22 patients stopped CPAP after a variable period of time; 10 patients died and one acromegalic patient was considered cured after hypophysectomy for a pituitary adenoma. Depending upon the definition of acceptable compliance, the compliance rate in this group was between 77% and 89%. The mean rate of use was correlated with indices of disease severity (apnea index, apnea+hypopnea index, minimal SaO2 during sleep, daytime PaO2, pulmonary artery pressure). Thirty-six nonapneic snorers accepted CPAP. In this group, 26 are still on CPAP, with a mean daily rate of use of 5.4 +/- 0.5 hours; one patient died; one underwent uvolopalatopharyngoplasty without follow-up; and eight stopped CPAP. The compliance rate in this group was between 58% and 78%. This study shows that CPAP is reasonably accepted by OSA patients as well as by nonapneic snorers.(ABSTRACT TRUNCATED AT 250 WORDS)

Nocturnal cortisol release in relation to sleep structure.

Abstract: The relationship between the temporal organization of cortisol secretion and sleep structure is controversial. To determine whether the cortisol profile is modified by 4 hours of sleep deprivation, which shifts slow-wave sleep (SWS) episodes, 12 normal men were studied during a reference night, a sleep deprivation night and a recovery night. Plasma cortisol was measured in 10-minute blood samples. Analysis of the nocturnal cortisol profiles and the concomitant patterns of sleep stage distribution indicates that the cortisol profile is not influenced by sleep deprivation. Neither the starting time of the cortisol increase nor the mean number and amplitude of pulses was significantly different between the three nights. SWS episodes were significantly associated with declining plasma cortisol levels (p less than 0.01). This was especially revealed after sleep deprivation, as SWS episodes were particularly present during the second half of the night, a period of enhanced cortisol secretion. In 73% of cases, rapid eye movement sleep phases started when cortisol was reflecting diminished adrenocortical activity. Cortisol increases were not concomitant with a specific sleep stage but generally accompanied prolonged waking periods. These findings tend to imply that cortisol-releasing mechanisms may be involved in the regulation of sleep.

Epidemiology of obstructive sleep apnea syndrome.

Abstract: Obstructive sleep apnea syndrome (OSAS) is the most common organic disorder of excessive daytime somnolence In cross-sectional studies the minimum prevalence of OSAS among adult men is about one per cent Prevalence is highest among men aged 40-65 years The highest figures for this age group indicate that their prevalence of clinically significant OSAS may be 85% or higher Habitual snoring is the most common symptom of OSAS (70-95%) The most significant risk factor for OSAS is obesity, especially upper body obesity Other risk factors for snoring, and for OSAS, are male gender, age between 40 and 65 years, cigarette smoking, use of alcohol, and poor physical fitness Upper airway obstruction with snoring or sleep apnea are commonly seen in children of all ages Snoring is very common among infants and children with Pierre Robin syndrome and among infants with nasal obstruction Snoring and obstructive sleep apnea are also very common in men with acromegaly Many other syndromes or diseases exist in which the upper airway is narrowed Prevalence of snoring and sleep apnea is increased in all such situations It has been suggested that sleep apnea may be one mechanism contributing to sleep-related mortality The prevalence of every night snoring seems to decrease after the age of 65 However, more than 25% of persons over 65 have more than five apneas per hour of sleep It remains to be seen whether this finding has clinical significance Partial upper airway obstruction, even without apneas, may influence pulmonary arterial pressure and may cause daytime sleepiness and some health consequences(ABSTRACT TRUNCATED AT 250 WORDS)

Sleep positions and position shifts in five age groups: an ontogenetic picture.

Abstract: In an attempt to characterize the development of sleep positions and position shifts in the human, 10 subjects (5 males and 5 females) in each of the following five age groups were studied: 3-5, 8-12, 18-24, 35-45 and 65-80 years old. Subjects slept for four consecutive nights (except the 3-5 year olds who slept two nights) in the laboratory where standard polysomnography was recorded. On nights 3 and 4, sleep positions were recorded with a Super 8 Camera taking one frame every 8 seconds and were scored using four dimensions (head, trunk, legs and arms) each consisting of four categories. The results revealed a significant ontogenetic decrease in the number of position shifts with averages of 4.4, 4.7, 3.6, 2.7 and 2.1 changes per hour, respectively. There was a corresponding progressive increase in the duration of positions and in the number of periods of more than 30 minutes of postural immobility. Whereas in children, prone, supine and lateral positions were assumed to occupy an equal proportion of sleep time, trend analyses revealed a significant progressive ontogenetic disappearance of prone positions and a progressive preference, very marked in the elderly, for right-side positions.

Slow wave sleep dreaming.

Abstract: Fifty volunteers slept two nonconsecutive nights in a sleep laboratory under electropolygraphic control. They were awakened for one report per night. Awakenings were made, in counterbalanced order, from slow wave sleep (SWS--stage 3-4 and stage 4) and rapid eye movement (REM) sleep. Following dream reporting, subjects were asked to identify memory sources of their dream imagery. Two independent judges reliably rated mentation reports for temporal units and for several content and structural dimensions. The same judges also categorized memory sources as autobiographical episodes, abstract self-references, or semantic knowledge. We found that REM reports were significantly longer than SWS reports. Minor content SWS-REM differences were also detected. Moreover, semantic knowledge was more frequently mentioned as a dream source for REM than for SWS dream reports. These findings are interpreted as supporting the hypothesis that dreaming is a continuous process that is not unique to REM sleep. Different levels of engagement of the cognitive system are responsible for the few SWS-REM differences that have been detected.

Melatonin rhythms in night shift workers.

Abstract: For some time, it has remained uncertain whether the circadian rhythms of permanent night shift workers are adapted to their night-active schedule. Previous studies of this question have often been limited by "masking" (evoked) effects of sleep and activity on body temperature and cortisol, used as marker rhythms. In this study, the problem of masking was minimized by measuring the timing of melatonin production under dim light conditions. Nine permanent night shift workers were admitted to the Clinical Research Center (CRC) directly from their last work shift of the week and remained in dim light while blood samples were obtained hourly for 24 hours. Melatonin concentrations were measured in these samples using a gas-chromatographic mass-spectrometric method. Sleep diaries were completed for two weeks prior to the admission to the CRC. Overall, the onset of the melatonin rhythm was about 7.2 hours earlier (or 16.8 hours later) in the night workers compared to day-active controls. It was not possible to know whether the phase of the melatonin rhythm was the result of advances or delays. In night shift workers, sleep was initiated (on average) about three hours prior to the onset of melatonin production. In contrast, day-active subjects initiated sleep (on average) about three hours after their melatonin onset. Thus, the sleep times selected by night shift workers may not be well-synchronized to their melatonin rhythm, assumed to mark the phase of their underlying circadian pacemaker.

A longitudinal study of sleep stages in young women during pregnancy and postpartum.

Abstract: We conducted a longitudinal polysomnographic study in five healthy primiparous subjects, whose sleep was first recorded between 8 and 16 weeks of gestation, then every 2 months until parturition and at 1 month postpartum. The first 6 hours of sleep were used for statistical analysis. In contrast to previous studies, we found no reduction in stage 4 sleep with pregnancy. Slow-wave sleep (comprising stages 3 and 4), was significantly higher at 27-39 weeks of gestation than at 8-16 weeks, as predicted by the restorative theory of sleep. There was no significant difference in rapid eye movement (REM) sleep time. When compared to a group of normal ovulating women, however, REM sleep time decreased during the last two months of pregnancy and, although there was no change in sleep onset latency, the time spent awake during the first six hours of sleep was increased. Future research into the effects of cortisol and progesterone is indicated.

Neurobehavioral manifestations in obstructive sleep apnea syndrome before and after treatment with continuous positive airway pressure.

Abstract: Obstructive sleep apnea syndrome (OSAS) is characterized by recurrent apneas during sleep, resulting in repetitive hypoxemic episodes and a constant interruption of the normal sleep pattern. Vigilance impairment and neuropsychological deficits are among the main symptoms seen in this condition. One of the major questions in this field concerns the reciprocal interactions between nocturnal hypoxemia, sleep disruption, excessive daytime sleepiness and cognitive deficits. Results of this study suggest that vigilance impairment is attributable mostly to nocturnal hypoxemia. However, in cognitive deficits, hypoxemia seems to play a major role in executive and psychomotor tasks, whereas attention and memory functions appear to be related to vigilance impairment. After treatment, hypoxemia-related deficits and some degree of sleepiness persist. These results raise the possibility of an irreversible anoxic central nervous system (CNS) damage in severe OSAS.

Isolated sleep paralysis elicited by sleep interruption

Abstract: We elicited isolated sleep paralysis (ISP) from normal subjects by a nocturnal sleep interruption schedule. On four experimental nights, 16 subjects had their sleep interrupted for 60 minutes by forced awakening at the time when 40 minutes of nonrapid eye movement (NREM) sleep had elapsed from the termination of rapid eye movement (REM) sleep in the first or third sleep cycle. This schedule produced a sleep onset REM period (SOREMP) after the interruption at a high rate of 71.9%. We succeeded in eliciting six episodes of ISP in the sleep interruptions performed (9.4%). All episodes of ISP except one occurred from SOREMP, indicating a close correlation between ISP and SOREMP. We recorded verbal reports about ISP experiences and recorded the polysomnogram (PSG) during ISP. All of the subjects with ISP experienced inability to move and were simultaneously aware of lying in the laboratory. All but one reported auditory/visual hallucinations and unpleasant emotions. PSG recordings during ISP were characterized by a REM/W stage dissociated state, i.e. abundant alpha electroencephalographs and persistence of muscle atonia shown by the tonic electromyogram. Judging from the PSG recordings, ISP differs from other dissociated states such as lucid dreaming, nocturnal panic attacks and REM sleep behavior disorders. We compare some of the sleep variables between ISP and non-ISP nights. We also discuss the similarities and differences between ISP and sleep paralysis in narcolepsy.

From obstructive sleep apnea syndrome to upper airway resistance syndrome: consistency of daytime sleepiness.

Abstract: Some patients with excessive daytime sleepiness who do not present the features of obstructive sleep apnea syndrome (OSAS) present a sleep fragmentation due to transient alpha EEG arousals lasting between three and 14 seconds. These transient EEG arousals are related to an abnormal amount of breathing effort, indicated by peak inspiratory esophageal pressure (Pes) nadir. In the studied population, these increased efforts were associated with snoring. Usage of nasal CPAP, titrated on Pes nadir values, for several weeks eliminated subjective daytime sleepiness and improved Multiple Sleep Latency Test scores from baseline evaluations. Patients suspected of CNS hypersomnia should be asked about continuous snoring, and their clinical evaluation should include a good review of maxillo-mandibular and upper airway anatomy.

Relations between sleep stage, posture and effective nasal CPAP levels in OSA

Abstract: A retrospective analysis of positional data from 100 male patients with obstructive sleep apnea (OSA) was conducted to determine whether or not 1) the degree of positional dependency was similar in rapid eye movement (REM) compared to non-REM (NREM) sleep, 2) positional dependency correlated with effective levels of nasal continuous positive airway pressure (CPAP) and 3) patients with positional OSA preferentially avoided sleeping in the supine position The apnea-hypopnea index (AHI) was scored separately for sleep state (NREM and REM) and for posture [off back (AHI-O) and on back (AHI-B)] The ratio of AHI-O/AHI-B was used to define positional OSA as AHI-O/AHI-B less than or equal to 050 (P group) and nonpositional OSA as 050 less than AHI-O/AHI-B (NP group) A group of 31 patients who had sufficient sleep time in NREM and REM sleep in both sleep postures was selected In this group 9 out of 22 subjects who showed positional dependency during NREM sleep became nonpositional during REM sleep (005 less than p less than 010) The mean effective nasal CPAP level was slightly, but significantly, lower in the P group than in the NP group (80 versus 91 cm H2O; p less than 005) In addition, a correlation between AHI and effective nasal CPAP levels was found (r = 0491; p = 00001) The P group had less supine sleep time (SST) than the NP group (32% versus 45% of total sleep; p less than 0005)(ABSTRACT TRUNCATED AT 250 WORDS)

Sleep propensity free-runs with the temperature, melatonin and cortisol rhythms in a totally blind person.

Abstract: In previous studies, we found that many totally blind people have free-running melatonin rhythms, but that free-running melatonin rhythms were not necessarily associated with periodic insomnia and daytime sleepiness Thus, it was not clear if the circadian sleep propensity rhythm was free-running with the other circadian rhythms In the present study, we report that the sleep propensity rhythm (as defined by an ultrashort sleep-wake schedule) free-ran with the melatonin, temperature and cortisol rhythms in a 44-year-old totally blind man even though he maintained a conventional sleep schedule and did not complain of clinically significant insomnia or excessive daytime sleepiness

Sleep architecture and sleep apnea in patients with Cushing's disease.

Abstract: Patients with Cushing's syndrome (CS) frequently have sleep complaints. We evaluated sleep polysomnographically in 22 patients, including 17 with pituitary-ACTH-dependent Cushing's disease (CD) and five with CS from an adrenal tumor. Data were compared to healthy controls of comparable age. Seven patients (32%) demonstrated at least mild sleep apnea (> or = 9.4 events/hour), and four of 22 (18%) had > or = 17.5 events/hour. The apneic CD and CS patients had a trend for a greater complaint of excessive daytime sleepiness. Both apneic and nonapneic groups had considerable snoring and obesity. The electroencephalographic (EEG) sleep of nonapneic patients was compared to that of normal subjects. Nonapneic CD patients differed strikingly from healthy volunteers in sleep continuity and architecture, demonstrating lighter, fragmented sleep. Rapid eye movement (REM) sleep in CD patients bore many similarities to the sleep of patients with major depression, with REM latency being significantly shortened and REM density significantly increased. Continued examination of EEG sleep in CD patients may shed light on similarities in pathophysiology between CD and major depression, disorders which are characterized by both a dysfunction of the hypothalamic-pituitary-adrenal axis and alterations in mood.

The evoked K-complex: all-or-none phenomenon?

Abstract: The functional significance and topographical variation of the different components of the evoked K-complex were examined. In the first experiment, the intensity of the stimulus (80 and 60 dB SPL) and its rise-and-fall time (2 and 20 milliseconds) were manipulated during nonrapid eye movement sleep. In the second experiment the tonal frequency (500, 1,000 and 2,000 Hz) of the stimulus was manipulated. In the first experiment, nine stimuli were presented every 10 seconds, whereas in the second, 20 consecutive stimuli were presented. The evoked K-complex consisted of two different negative components peaking at approximately 350 and 550 milliseconds, respectively, and followed by a positive component peaking at approximately 900 milliseconds. K-complexes were easier to elicit for high-intensity fast rise-and-fall time stimuli than for low-intensity slow rise-and-fall time stimuli. The probability of occurrence was not affected by the tonal frequency of the stimulus. When a K-complex was evoked, the amplitude and latency of N350, N550 and P900 remained invariant regardless of its intensity, rise-and-fall or its tonal frequency. The N550-P900 portion of the K-complex therefore appears to be an all-or-none phenomenon. On trials in which a K-complex could not be elicited, N350 was still visible although much attenuated. In these trials, its amplitude was further reduced when stimulus intensity was lowered. N350 might need to reach a certain critical threshold before the much larger N550-P900 complex is elicited.

Sleep disturbances in men with asymptomatic human immunodeficiency (HIV) infection.

Abstract: During the clinical latency phase of human immunodeficiency virus (HIV) disease the central nervous system may be infected and begin to manifest subtle dysfunction. Our early investigations demonstrated persistent alterations in the sleep architecture of HIV-infected asymptomatic men. The major aims of this study were to delineate alterations of sleep architecture in asymptomatic HIV-infected men, to identify and describe sleep behavior complaints and to seek a correlation between objective sleep parameters and subjective complaints of sleep behavior. The study sample consisted of 24 men, 14 HIV-infected and 10 HIV-negative, age-matched controls. The protocol included a comprehensive history and physical, two polysomnograms, urine toxicity, detailed written sleep questionnaire, the Pittsburgh Sleep Quality Index, the Spielberger State-Trait Anxiety Test and the Beck Depression Inventory. Our results indicated that sleep architecture differed from controls in that wakefulness, slow-wave sleep [SWS-stage 3 and 4 nonrapid eye movement (NREM) sleep] and stage rapid eye movement (REM) sleep were more evenly dispersed throughout the night. In particular, SWS was prevalent during the second half of recorded sleep. The observed changes in the NREM/REM cycle could not be explained on the basis of underlying psychopathology. Just as the course of individuals with HIV infection varies, it is expected that sleep abnormalities will vary. Considering the known relationships between NREM stage 3 and 4 and immune system function, it is possible that the observed alterations in the NREM/REM cycle are related to coincident changes in immunologic function. Quantitative measures of NREM sleep, especially SWS and REM sleep, are perhaps of greater significance than relative measures of sleep stages.(ABSTRACT TRUNCATED AT 250 WORDS)

Daily Social Rhythms in the Elderly and Their Relation to Objectively Recorded Sleep

Abstract: This study tested the hypothesis that the impaired sleep of healthy 71-91 year olds might be due to circadian dysfunction stemming from irregularity of life-style. Twenty-five old women, 20 old men and 21 young controls (19-28 years old) were studied in relation to 1) objective sleep as measured in the laboratory, 2) subjective sleep quality as measured by the Pittsburgh sleep quality index (PSQI) and 3) the social rhythm metric (SRM), an instrument to quantify the daily rhythms of life. Contrary to prediction, the SRM scales revealed that the older group had just as many activities completed and just as much other-person involvement as the young. Moreover, they showed a significantly greater regularity in daily life-style than the young, despite showing reliably impaired subjective and objective sleep. This suggests either that these seniors have always been regular in their life-style and that this has been protective of their health and vigor, or that their regularity has been developed as an adaptive response to age-related changes in the circadian system.

Age-related differences in recovery from simulated jet lag.

Abstract: Six healthy young men and eight early middle-aged men were isolated from environmental time cues for 15 days. For the first 6-7 days (one or two nights adaptation, four nights baseline), their sleep and meals were scheduled to approximate their habitual patterns. Their daily routines were then shifted 6 hours earlier by terminating the sixth or seventh sleep episode 6 hours early. The new schedules were followed for the next 8 or 9 days. Important age-related differences in adjustment to this single 6-hour schedule shift were found. For the first 4-day interval after the shift, middle-aged subjects had larger increases of waking time during the sleep period and earlier termination of sleep than young subjects. They also reported larger decreases in alertness and well-being and larger increases in sleepiness, weariness and effort required to perform daily functions. The rate of adjustment of the circadian core temperature rhythm to the new schedule did not differ between groups. These results suggest that the symptoms reported by the middle-aged subjects may be due mainly to difficulty maintaining sleep at early times of the circadian day. The compensatory response to sleep deprivation may also be less robust in middle-aged individuals traveling eastbound.

Comparison of EEG Sleep Measures in Healthy Full-Term and Preterm Infants at Matched Conceptional Ages

Abstract: Continuous electroencephalogram (EEG) sleep studies were obtained on healthy full-term and preterm infants at matched conceptional ages. Studies were recorded under environmentally controlled conditions. Eighteen healthy preterm infants were matched to 18 full-term infants based on conceptional age, sex, race and socioeconomic class. The initial 3 hours of a 12-hour recording were simultaneously recorded on paper and computer. The visually scored data based on the paper recordings for sleep architecture and continuity measures were studied. Differences in each sleep organization for the preterm infants included the following: a longer ultradian sleep cycle (70 minutes vs. 53 minutes, p = 0.02) was noted. More abundant trace alternant (34% vs. 28%, p = 0.02) and less abundant low-voltage irregular active sleep (13% vs. 17%, p = 0.05) were noted. Although no differences were observed for sleep latency and efficiency, the preterm infants had fewer numbers and shorter durations of arousals, fewer body movements and rapid eye movement (REM) (p < 0.01), particularly during quiet sleep. The extrauterine experience or the earlier birth of the preterm infant may influence specific sleep architecture and continuity measures when compared with the sleep of full-term infants who experienced a complete intrauterine gestation.

Multiple sleep latency tests during the constant routine.

Abstract: The "post-lunch dip" is a common behavioral phenomenon, though perhaps a misnomer. Biphasic models of the human sleep tendency rhythm suggest an alternative explanation for the afternoon decline in alertness. Sleep tendency was measured with the Multiple Sleep Latency Test (MSLT) at 2-hour intervals in 16 volunteers from three age groups (ages 10-12, ages 16-17, ages 62-74 years) during a constant routine in which small meals were given each hour. Baseline scores showed no significant Time of Day effect, although a trend for an afternoon dip was present in the eldest group. During the constant routine, a significant Time of Day effect was found for the two older groups and not for the prepubertal group. The results indicate a midday increase in sleep tendency that is unrelated to food intake but that may be related to developmental or maturational processes.