Showing papers in "Sleep in 1988"

Catastrophes, sleep, and public policy: consensus report

Abstract: Following the 1986 annual meeting of the Association of Professional Sleep Societies (Columbus, Ohio, U.S.A., June 15–22, 1986), a committee of scientists was formed to review recent reports and related information on the role of human sleep and brain clocks (time-of-day variation in physiology and alertness) in the occurrence of medical and human error catastrophes. This is a report of the committee's findings and recommendations. The committee evaluated scientific and technical reports on the distribution throughout the 24-h day of medical incidents (such as heart attack and stroke) and performance failures (such as vehicular accidents and human errors in industrial and technical operations that can affect public safety). We found that these events occur most often at times of day coincident with the temporal pattern of brain processes associated with sleep. It thus appears that the occurrence of a wide range of catastrophic phenomena are influenced by sleep-related processes in ways heretofore not fully appreciated. The committee recognizes that there are now some efforts to assess the influence of sleep-related processes on performance in key sectors of our society. For example, the United States military participated in the NATO seminar entitled “Sleep And Its Applications for the Military” (Lyon, France, March 16–17, 1987). An obvious and major concern in connection with military applications is the possibility of human error in performance or judgment when dealing round-the-clock with allied and adversarial personnel and weapons systems located in many time zones all over the earth. The committee recommends an increase in the number and scope of such exercises to develop awareness in both the public and private sectors of the vulnerability of humans to suffer catastrophes as a function of these processes. We also recommend the development of policies within appropriate government agencies to facilitate the study of these processes, the application of measurements to identify sleep-related risks in the workplace, and the adoption of countermeasures to minimize their detrimental influence on human welfare and public safety.

Sleepiness as a consequence of shift work.

Abstract: The results reviewed clearly demonstrate that shift work is associated with increased subjective, behavioral, and physiological sleepiness. Apparently, the effects are due to combined circadian and homeostatic (sleep loss) influences. Sleepiness is particularly pronounced during the night shift, and may terminate in actual incidents of falling asleep at work. In some occupations this clearly constitutes a hazard that may endanger human lives and have large economic consequences. These risks clearly involve a larger number of people and should be of great significance to society.

Sleep Loss and “Divergent” Thinking Ability

Abstract: Although much is known about the impact of sleep loss on many aspects of psychological performance, the effects on divergent ("creative") thinking has received little attention. Twelve subjects went 32 h without sleep, and 12 others acted as normally sleeping controls. All subjects were assessed on the figural and verbal versions of the Torrance Tests of Creative Thinking. As compared with the control condition, sleep loss impaired performance on all test scales (e.g., "flexibility," the ability to change strategy, and "originality," generation of unusual ideas) for both versions, even on an initial 5-min test component. In an attempt at further understanding of whether these findings might be explained solely by a loss of motivation, two additional short and stimulating tests were also used--a word fluency task incorporating high incentive to do well and a challenging nonverbal planning test. Performance at these tasks was still significantly impaired by sleep loss. Increased perseveration was clearly apparent. Apparently, 1 night of sleep loss can affect divergent thinking. This contrasts with the outcome for convergent thinking tasks, which are more resilient to short-term sleep loss.

Daytime alertness in patients with chronic insomnia compared with asymptomatic control subjects.

Abstract: Despite the subjective reports of patients with difficulty initiating and maintaining sleep (DIMS) that they are impaired during the day, consistent differences in daytime functions have not been found between normal sleepers and patients with insomnia. The present study compares polysomnography and Multiple Sleep Latency Test (MSLT) data from 70 clinic patients seeking evaluation for chronic insomnia with data from a group of 45 asymptomatic sleepers. The DIMS group was found to sleep significantly less than the control group; yet they were also significantly more alert than the control group the following day, as measured by MSLT. Within the insomnia diagnostic subgroups, a correlation of -0.67 (p less than 0.05) was found between nocturnal total sleep time and mean MSLT. The results are interpreted as supporting the existence of a tendency towards physiological hyperarousal in patients with chronic insomnia. This tendency may be exacerbated by other factors (e.g., personality disorder, periodic leg movements) also associated with insomnia.

Night-to-night variability in sleep apnea and sleep-related periodic leg movements in the elderly.

Abstract: The amount of night-to-night variability in sleep apnea (SA) and sleep-related periodic leg movements (PLMs) is largely unknown but, despite this, clinical decisions are based on single-night studies in many clinical sleep laboratories. We examined variability in SA and PLMs over three nights in 46 community-resident seniors. No evidence was found for either a first-night effect or a directional trend across nights in either the Respiratory Disturbance Index (RDI) or the Movement Index (MI), despite a prominent first-night effect on pattern of sleep. Duration of apneas/hypopneas and degree of associated heart rate change and oxygen desaturation in subjects with SA and intermovement interval in subjects with PLMs also failed to show systematic change across nights. However, if a cut-off score of 5/h for RDI and MI was used, the classification recorded on the first night did differ from the classification given on at least one of the other nights in 43% of the subjects. The magnitude of fluctuation in RDI or MI from night to night was large enough in some subjects that, in a clinical situation, decisions based on one night would have been entirely different had the subject been studied on a different night. Night-to-night variability in RDI and MI within subjects also was associated with significant alterations in the sleep pattern. We conclude that caution should be taken in drawing conclusions from single-night studies, especially in individuals with relatively mild forms of SA and PLMs where nightly variations could easily place them above or below an arbitrary cut-off score.

Sleep patterns and stability in perimenopausal women

Abstract: Women between the ages of 40 and 59 years were classified as pre-, peri-, and postmenopausal, with and without hot flash symptoms, for comparison of somnographic sleep variables. Few differences in sleep variables were noted between the groups. However, peri- and postmenopausal women experiencing hot flashes (symptomatic) tended to have lower sleep efficiencies than those not experiencing hot flashes. As well, rapid-eye-movement (REM) latency was longer (p less than 0.05) in the symptomatic women (means = 94.2 min) than in the nonsymptomatic women (means = 71.4 min). Although an age difference existed between the menopausal status groups, it was less than a decade and a main group effect for sleep efficiency and REM latency was seen while controlling for age and/or depression.

Sleep need in adolescents: a longitudinal approach.

Abstract: A sample of 190 male and female "high school" students completed a sleep questionnaire for the first time when they were 10 to 14 years old. The survey was repeated five times at 2 year intervals. Ninety-three subjects answered the questionnaire each time. Subjective sleep need was assessed by the indicated wish for more sleep. The wish for more sleep was very pronounced, varying between 54.3% and 74.5% across the years. Individual consistency, however, was low since only 14.5% of the adolescents indicated the wish for more sleep in each survey, emphasizing the state dependency of this variable. Within each total sample, subjects with the wish for more sleep (MSL) and with sufficient sleep (SSL) were compared. Subjective sleep need was consistently validated by a syndrome of morning-tiredness. In the last two surveys, there was reduced time in bed (TIB) on weekdays in MSL subjects and longer TIB during vacation in surveys 2 through 5. Furthermore, MSL subjects more often showed irregular sleep habits. The previous sleep history of the MSL subjects in the last survey indicated that concomitants of the wish for more sleep were already experienced earlier in adolescence. The desired sleep duration of these subjects was 1.7 h longer than their current sleep on weekdays, an amount they had not obtained on weekdays since early adolescence. It is concluded that a substantial proportion of the adolescents seem to have had difficulties adapting to the general sleep time reduction occurring in adolescence.

Identifying Sleep Apnea from Self-Reports

Abstract: An apnea score (AS) was developed as a potential screening tool for sleep apnea This was based on self-report questionnaire responses of 76 sleep disorder center patients and 20 sleep survey volunteers Twenty volunteers and 23 patients (group I) comprised the initial AS development group Their questionnaire responses were compared to polysomnographic apnea indexes (AI) and apnea plus hypopnea indexes (AHI) Stepwise multivariate discriminant analysis was used to test whether or not selected group I questionnaire responses could be used to correctly classify respondents into apnea (AI or AHI greater than 5) or nonapnea (AI, AHI less than or equal to 5) groups Self-reports of "stops breathing during sleep," "loud snoring," and history of adenoidectomy best discriminated normal (AI less than or equal to 5) from apnea (AI greater than 5) cases The AS derived from group I responses to these three variables was then computed for group II (n = 53) After examination of the AS results, the AS was modified to include just "stops breathing" and "loud snoring" and the AI criterion was raised to 10 per hour This revised AS correctly identified 100% of the cases with moderate-severe sleep apnea (AI or AHI greater than 40) and 70-76% of all sleep apnea cases with AI or AHI greater than 5 Predictive accuracy was 88% for AI greater than 10 The two questions that comprise the AS should be incorporated into risk appraisal instruments or interviews to screen for sleep apnea

Sleep Apnea and Body Position during Sleep

Abstract: In patients with obstructive sleep apnea, it is believed that body position influences apnea frequency. Sleeping in the lateral decubitus position often results in significantly fewer apneas, and some have recommended sleeping on the side as the major treatment intervention. Previous studies, although calculating apnea-hypopnea index (AHI) for supine and lateral decubitus positions, have not taken sleep stage into account. To examine the effect of both sleep stage and body position on apnea duration (AD) and frequency, we determined AHI and AD in all spontaneous body positions during rapid eye movement (REM) and non-REM (NREM) sleep by reviewing videotapes and polysomnograms from 11 overnight studies of 7 obese patients with severe sleep apnea. Consistent with previous work, AD was significantly longer in REM then in NREM (32.5 +/- 2.3 s versus 23.5 +/- 1.9 s; p less than 0.05). This difference persisted when adjusting for body position. AHI was greater on the back than on the sides (84.4 +/- 4.9/h versus 73.6 +/- 7.5/h, p less than 0.05), but after accounting for sleep stage, this difference remained only for NREM (103 +/- 4.8/h versus 80.3 +/- 9.2/h, p less than 0.05) and not for REM (83.6 +/- 5.3/h versus 71.1 +/- 4.2/h, p NS). Although reduced, AHI on the sides still remained clinically very high. Body position changed frequently throughout the night, but some patients spent little or no time on their back. We conclude that AD is longer in REM than NREM, regardless of position, and AHI is higher on the back only in NREM. As AHI remains very high on the sides, favoring the lateral decubitus position may not be as beneficial as previously thought in very obese patients. Less obese patients are more likely to benefit by position changes.

Daytime sleepiness in young adults.

Abstract: The daytime sleepiness of a large sample (n = 129) of healthy, young (age 18-29) adults with no sleep-wake complaints was measured and compared with that of a sample (n = 47) of older (age 30-80) healthy, normal sleeping, subjects. Each spent 8 h in the laboratory on 1 night and received the Multiple Sleep Latency Test (MSLT) the following day. Sleep latency was measured at 1000, 1200, 1400, and 1600 h. Mean sleep latency ranged from 2 to 20 min within each group, but the shape of the distribution of latency between groups was different. The mean latency of young subjects (particularly college students) was shorter than that of the older subjects, with the differences occurring between the sleepiest 80% of each distribution. Among the college students, those with higher nocturnal sleep efficiencies (the previous night) were sleepier the following day than those with lower sleep efficiencies. The relation between nocturnal sleep efficiency and daytime sleepiness suggests that the increased sleepiness of average young adults is due to mild sleep restriction.

Role of Protriptyline and Acetazolamide in the Sleep Apnea/Hypopnea Syndrome

Abstract: The role of drug therapy in the treatment of the sleep apnea/hypopnea syndrome is unclear. In a randomised, double-blind, placebo-controlled study, we investigated the value of 14-day therapy with protriptyline (20 mg daily) or acetazolamide (250 mg 4 times per day) on symptoms and on the frequency of apneas, hypopneas, arousals, and 4% desaturations in 10 patients with obstructive sleep apnea/hypopnea syndrome. Overall, protriptyline did not have a significant effect either on symptoms or on any of the above polysomnographic criteria. Acetazolamide reduced the apnea/hypopnea frequency [placebo 50 +/- 26 (SD); acetazolamide 26 +/- 20/h of sleep, p less than 0.03] and tended to decrease the frequency of 4% desaturations (placebo 29 +/- 20; acetazolamide 19 +/- 16/h of sleep, p = 0.06). Despite these physiological improvements, acetazolamide did not significantly improve symptoms and paraesthesiae were common. Contrary to earlier studies, we conclude that protriptyline may have a limited role in the treatment of the sleep apnea syndrome. The reason why acetazolamide produced a physiological, but not a symptomatic, response requires further investigation.

Disturbed sleep while being on-call: an EEG study of ships' engineers.

Abstract: In order to investigate the effects of on-call duty on sleep and wakefulness, five male ships' engineers were studied using electroencephalogram (EEG) and electrocardiogram (ECG) recordings and subjective ratings. Sleep during on-call nights (two alarms) was shortened and contained less slow wave sleep (SWS) and rapid eye movement (REM) sleep, lower spectral power density, and a higher heart rate. Many of the effects were observable before any alarms had occurred. Rated sleep quality was lower, and sleepiness was higher during the subsequent day. It was suggested that the effects were due to apprehension/uneasiness induced by the prospect of being awakened by an alarm.

Passive body heating and sleep: influence of proximity to sleep

Abstract: Previous studies have found enhanced delta sleep following body heating. This study assessed the influence of body heating as a function of its proximity to sleep. Electroencephalogram (EEG) sleep patterns were compared following body heating (1 h immersion in water at 41 degrees C) at each of four times of day: morning (MO), afternoon (AF), early evening (EE), and late evening (LE), ending just prior to sleep. A delta filter/integrator system provided objective measures of delta content. Relative to baseline nights, whole-night delta sleep was increased by the two evening heating sessions only, particularly LE heating. Following LE, the increased delta occurred primarily in the first sleep cycle, whereas EE heating elicited increased delta distributed across the later sleep cycles (cycles 2-4). Effects on manually staged indices of slow wave sleep (SWS) were confined to increases in Stage 4 in the first sleep cycle following LE heating. Heating just prior to sleep also resulted in a substantial reduction in the duration of the first rapid eye movement sleep period. Sleep onset time was reduced by heating, particularly EE heating. The results indicate that body heating induces temporary changes that affect sleep propensity and both the quantity and temporal distribution of delta activity in the sleep EEG.

Cardiac and respiratory patterns in normal infants and victims of the sudden infant death syndrome.

Abstract: Victims of the sudden infant death syndrome (SIDS) have higher overall heart rates prior to death than do control infants (1). The objective of this study was to partition these heart rate differences by state and to identify any state-dependent differences in heart rate variability and respiratory rate and variability. Twenty-two recordings of electrocardiogram (ECG) and respiration from 16 infants who subsequently died of SIDS were compared with 66 recordings of age-matched control infants. Median cardiac and respiratory rate and variability were computed for each sleep state in each recording, and one-way analysis of variance tests were performed for each variable for infants less than 1 month and for infants greater than 1 month of age. Heart rate was higher in SIDS victims less than 1 month of age than in age-matched controls during all sleep-waking states. SIDS victims greater than 1 month showed higher heart rates during rapid eye movement sleep only. Heart rate variability was also diminished during waking in victims less than 1 month, but much of this difference could be attributed to increased heart rate. These results suggest that, as a group, SIDS victims differ physiologically from control infants and that these differences may be especially prominent during particular sleep-waking states.

Destructive bruxism: sleep stage relationship.

Abstract: Despite apparent similar amounts of bruxism, two groups that had been evaluated polysomnographically differed dramatically in symptomatology. Patients with severe symptoms were referred to as the destructive bruxism group and were compared with (a) a group with sleep disturbance complaints who had bruxism and (b) a group of insomniac depressed patients chosen without regard to bruxism. It was hypothesized that not only the presence of bruxism during sleep but its pattern and sleep stage relationship were factors affecting clinical symptoms. The results indicated that the sleep stage relationship was an important factor. Patients with severe symptoms attributed to nocturnal bruxism were likely to have more bruxism in REM sleep than the other groups. These results if replicated prospectively would help explain some of the discrepancies in the literature concerning sleep stage relationship of bruxism, as well as help explain differences in symptomatology of bruxism patients.

Evaluation of First Night Effect using Ambulatory Monitoring and Automatic Sleep Stage Analysis

Abstract: Home sleep recordings were conducted over three consecutive nights in 12 normal subjects using the Oxford Medilog 9000 system and automatic sleep stage analysis. The equipment was well tolerated and adequate sleep recordings were obtained on each test evening. The results showed that there was no significant differences over the three nights for any of the sleep parameters measured.

Test-retest reliability of the MSLT.

Abstract: The test-retest reliability of the Multiple Sleep Latency Test (MSLT) was evaluated in 14 healthy normal subjects. Each slept a single night in the laboratory (8 h time in bed) and received the MSLT the following day (1000, 1200, 1400, and 1600 h) on two occasions separated by 4-14 months. Mean sleep latency (four tests) was highly reliable from MSLT to MSLT (r = 0.97, p less than 0.001). The test-retest reliability did not change as a function of the interval of time between tests or as a function of the level of sleepiness (range = 4-20 min) within the population. However, as the number of tests comprising the MSLT was reduced below three, the reliability was reduced such that only 50% or less of the variance could be predicted.

Sleep and waking states in infancy: normative studies.

Abstract: Twelve-hour polygraphic recordings were obtained in 20 normal healthy term infants at 1 week of age, at monthly intervals up to 4 months, and at 6 months of age. Each minute of these recordings was coded into active sleep (AS), quiet sleep (QS), wakefulness (AW), or indeterminate (IN) based on polygraphic and behavioral variables. For each state, a dozen variables were computed with the help of a laboratory computer. Together these variables describe trends in the development of sleep and wakefulness in the laboratory: an increase in QS and a concomitant decrease in AS, an increase in sustained episodes of these states, and continuous sleep onset in AS throughout this time span. Considerable variability appears to characterize immature sleep patterns, but a reduction in variability was noted between 3 and 4 months of age. The number of sustained sleep-state episodes and the percentage of AS and IN proved to be stable characteristics of individual infants. The large variability among and within infants sheds doubt on the usefulness of polygraphic monitoring of sleep states for early detection of abnormalities.

Distribution of choline acetyltransferase immunoreactive somata in the feline brainstem: implications for REM sleep generation.

Abstract: In the present study we examined the distribution of cholinergic and catecholaminergic neurons, in the feline brainstem, as defined by choline acetyltransferase (ChAT) and tyrosine hydroxylase (TH) immunohistochemistry. In the dorsal tegmentum, ChAT immunoreactive neurons were distributed in the parabrachial area [the pedunculopontine group (PPG)] and along the medial adjacent central gray [the lateral dorsal tegmental group (LDT)]. The cholinergic neurons in the LDT area were larger than those in the PPG. When adjacent tissue sections were labeled with TH we noted extensive overlap between catecholamine and cholinergic neurons in the PPG, suggesting that REM sleep may occur as a result of an interaction between these transmitters in this area rather than the medial pontine reticular formation where no cholinergic or catecholamine neurons were found. Cholinergic neurons were also found in the cranial nerve nuclei and the nucleus ambiguus. The presence of cholinergic neurons in the PPG and LDT suggest that these neurons may play an important role in the generation of some of the tonic and phasic components of REM sleep, such as cortical desynchronization, pontogeniculo occipital waves, and muscle atonia.

Effect of continuous heat exposure on sleep stages in humans.

Abstract: Six young men were exposed to a thermoneutral environment of air temperature (Ta) 20 degrees C for 5 days and nights followed by an acclimation period of 5 days and nights at Ta 35 degrees C and 2 recovery days and nights at Ta 20 degrees C. Electrophysiological measures of sleep, esophageal temperature, and mean skin temperature were continuously monitored. The total nocturnal body weight loss was measured by a sensitive platform scale. Compared with the 5 nights of the baseline period at 20 degrees C, sleep patterns showed disturbances at 35 degrees C. Total sleep time was significantly reduced, while the amount of wakefulness increased. The subjects exhibited fragmented sleep patterns. The mean duration of REM episodes was shorter at 35 degrees C than at 20 degrees C of Ta, while the REM cycle length shortened. In the acclimation period, there was no change in sleep pattern from night to night, despite adaptative adjustments of the thermoregulatory response. The protective mechanisms of deep body temperature occurring with heat adaptation did not interact with sleep processes. Upon return to baseline condition, a recovery effect was observed on a number of sleep parameters which were not significantly affected by the preceding exposure to prolonged heat. This would suggest that during exposure to dry heat, the demand for sleep could overcome that of other regulatory functions that are temperature-dependent. Therefore, a complete analysis of the effect of heat on sleep parameters can be assessed only if heat exposure is compared with both baseline and recovery periods.

Cognitive function in middle-aged snorers and controls: role of excessive daytime somnolence and sleep-related hypoxic events.

Abstract: Association of snoring and cognitive function was studied in 46 habitually snoring men ages 41-52 years, and 60 occasionally or never-snoring control male subjects of the same age group Sleep recordings with monitoring of apneas and hypopneas were made with the static-charge sensitive bed method Blood oxygen saturation was measured with an oximeter and the snoring sounds were recorded with a microphone after clinical and neuropsychological assessment A questionnaire with items on excessive daytime somnolence (EDS), sleep, and snoring quality was also used EDS (as measured by items on the questionnaire) associated with tests requiring concentration, memory retention, and verbal and spatial skills in the habitual snorers group The number of oxygen desaturation episodes exceeding 4% associated with defective delayed Recall of Logical Stories of the Wechsler Memory Scale and with spatial orientation (Clock test) in the habitual snorers' group even after adjusting for age and obesity

Altitude insomnia: studies during an expedition to the Himalayas.

Abstract: During an expedition to the Himalayas, we studied the sleep and respiration of six climbers. Three ingested acetazolamide (500 mg) daily throughout the climb and the other three ingested placebo. At high altitude (4,150-4,846 m), each subject ingested temazepam (10 mg) for one night and placebo for another. Acetazolamide improved sleep above 2,750 m, but it is uncertain whether this was due to sedation or to improvements in arterial oxygen saturation. Sleep was markedly disturbed in all subjects above 4,000 m. Temazepam improved sleep, and in subjects taking acetazolamide, it reduced sleep-onset latencies and increased sleep efficiency close to that of sea level values. These observations suggest that the prophylactic use of acetazolamide is likely to improve sleep in climbers and that a low dose of a benzodiazepine such as temazepam (10 mg) may be beneficial at high altitude. Studies are now needed to exclude any possibility of respiratory impairment at altitude before a firm recommendation can be made regarding the routine use of this hypnotic.

Nocturnal oscillations in plasma renin activity and REM-NREM sleep cycles in humans: a common regulatory mechanism?

Abstract: To establish the strength of the relationship between the nocturnal oscillations in plasma renin activity (PRA) and the sleep stage patterns, 42 PRA profiles from blood collected at 10-min intervals and the concomitant polygraphic sleep recordings were analyzed. In all cases, PRA curves exactly reflected the pattern of sleep stage distribution. When sleep cycles were complete, PRA levels oscillated at a regular 100-min period, with a strong spectral density. Declining PRA levels always coincided with REM sleep phases and increasing levels with NREM sleep phases. More precisely, peak levels corresponded to the transition from deep sleep stages toward lighter ones. The start of the rises in PRA generally marked the transition from REM sleep to stage 2. For incomplete sleep cycles, PRA curves reflected all disturbances and irregularities in the sleep structure. Spontaneous and provoked awakenings blunted the rise in PRA normally associated with NREM sleep, which indicates that disturbing sleep modifies the renin release from the kidneys. These results suggest that a common mechanism within the central nervous system controls both PRA oscillations and the REM-NREM sleep alternation.

Factor analysis of the St. Mary's Hospital Sleep Questionnaire.

Abstract: The St. Mary's Hospital Sleep Questionnaire was designed to evaluate the sleep of hospital patients. To gain an understanding of possible underlying factors, the questionnaire was factor analysed using data collected from 222 hospitalised rheumatic patients. The analysis did not produce a completely clear factor structure. Two factors relating to "sleep latency" and "sleep quality" emerged more clearly than the other factors produced. These factors correspond with two sleeping state factors (ease of getting to sleep; quality of sleep) that were extracted by a previous factor analysis of the Leeds Sleep Evaluation Questionnaire. This suggests that the two most important aspects of subjectively perceived sleep are the process of going to sleep and the quality of sleep.

The effect of total sleep deprivation on plasma melatonin and cortisol in healthy human volunteers.

Abstract: Twelve healthy volunteers were included in this study. Baseline curves for melatonin and cortisol were obtained after one night of adaptation to laboratory conditions. From 10:00 p.m. to 6:00 a.m., blood samples were drawn every hour. On the third night, the subjects were kept awake at the sleep unit. Curves for the two hormones were then obtained after 36 h of total sleep deprivation (SD). The levels of these hormones were evaluated by calculating the area under the curve at each hour in both situations (basal and after sleep deprivation). It was found that the melatonin levels were increased after sleep deprivation, whereas the cortisol levels remained the same. These results suggest a mechanism by which a reset of abnormal rhythms can occur in depression.

Increasing the functional residual capacity may reverse obstructive sleep apnea.

Abstract: We describe the reversal of obstructive sleep apnea with a 0.5 L increase in the functional residual capacity (FRC) in a patient with sleep apnea syndrome. The patient had been treated with medroxyprogesterone acetate for 8 months. The increase in FRC was obtained by applying a constant negative extrathoracic pressure (NEP) with a poncho-type respirator. With pulmonary inflation, there was a dramatic decrease in the apnea index and the percent apnea time, and an improvement in sleep architecture. At all sleep stages, the desaturation duration was shorter with NEP. The exact mechanisms by which pulmonary expansion improved sleep apnea in this patient remain unclear; lung volume dependence of upper airway patency and the improvements in apnea-induced desaturation may be contributing factors. Our observation illustrates that lung volumes may be an important factor in the pathophysiology of obstructive sleep apnea, especially in the apnea onset and in the apneic-induced desaturation.

Perception of waking and sleeping: possible implications for the evaluation of insomnia.

Abstract: Perception of awakening, its connection to electroencephalogram (EEG), and its significance for morning recall were studied in insomniacs and normals. Fourteen insomniacs and 14 age- and sex-matched controls kept a sleep log for 1 week and slept once in the laboratory (standard polygraphy). In addition, actual perception of awakening was measured by a behavioral device. Results suggest that physiological arousal is necessary, but not sufficient, for perception of awakening. Many arousals that are not perceived occur during the first REM-NREM cycle. Insomniacs nearly exclusively perceive those arousals occurring after consolidated sleep (at least 15 min) and at the beginning of interrupted sleep intervals. It is suggested that insomniacs perceive these intervals as continuous wakefulness and have difficulty in perceiving short-lasting sleep, whereas controls often do not perceive wakefulness at all. The latter may be a sleep-protecting mechanism. Number and correlation suggest that recalled awakenings are exactly those perceived. The connection between physiological and experimental subjective data is discussed.

Episodic nocturnal wanderings in non-epileptic young patients

Abstract: Twelve patients, aged 19 to 29 years, presented with episodic nocturnal wanderings characterized by stereotyped frequent attacks of screaming, ambulation, and complex automatisms during sleep. The attacks ranged in frequency from two or three per year to several per night and were often associated with semi-purposeful violent and even life-threatening behavior. None of the patients had a history of seizures; three had a history of prior parasomnias and four had family members with a history of parasomnia. Polysomnographic and daytime electroencephalographic (EEG) investigations showed potentially epileptiform activity in four patients. Recorded episodes were not accompanied by ictal EEG activity. Anticonvulsant medication reduced or eliminated the attacks in all of the nine treated patients. The pathophysiology of the disorder is uncertain.

Behavioral Versus EEG-Based Monitoring of All-Night Sleep/Wake Patterns

Abstract: Faint tones were presented at intervals (average 16 s) throughout a night's sleep; whenever they heard them, subjects pressed a palm-mounted button to switch them off. At the same time, electroencephalogram (EEG) was recorded. Button-press responses occurred in all EEG stages of sleep except Stage 4, although there was only one behavioral response (BR) in Stage 3 and one in REM. The mean probability of response (PR)/Stage was Stage 1 = 0.235, Stage 2 = 0.016, Stage 3 = 0.001, Stage 4 = 0.000, Stage REM = 0.0004. Also, responses sometimes failed to occur in EEG Stage wake (PR = 0.94), particularly near sleep onset. If the criterion for wakefulness is cognitive response to external stimulation, only in EEG Stages 3, 4, and REM can accurate distinctions between sleep and wakefulness be made. If EEG is the criterion, then the data suggest that cognitive response is possible during Stages 1 and 2 "sleep." The concept of a sleep onset period (SOP), characterized by lengthening response times and intermittent response failure (thereby reflecting neither true sleep or wakefulness), may provide a useful resolution of this definitional dilemma.