All-night Sleep Research Articles

Major unipolar depression and mild Alzheimer's disease: differentiation by quantitative tonic REM EEG

In a previous report, tonic REM sleep epochs from the all-night sleep EEG were processed and analyzed to produce a diagnostic that discriminated mild Alzheimer's disease (AD) from cognitively unimpaired control subjects. Here, we examine the specificity of this diagnostic in distinguishing depression from AD. Twenty-four cognitively unimpaired seniors (aged 63±1.3) with major depressive disorder (unipolar) were monitored for all-night EEG in a manner identical to that used in our previous report. Tonic REM EEG epochs were preconditioned, spectrally analyzed and compated with known populations of control and AD EEG spectra. Instances when a given depressed subject's spectra fell within spectral zones unique to control or AD populations formed a diagnostic score (control, AD, neither of these). Diagnostic scores correctly identified 88% ( 21 24 ) of cognitively unimpaired seniors with major depressive disorder (unipolar). This can be compared with 89% ( 31 35 ) of mild AD subjects and 100% ( 43 43 ) of control subjects correctly identified in our previous report. This diagnostic also correctly classified as to eventual clinical AD/not AD outcome 8 subjects with both major depressive disorder and validated memory complaints. The diagnostic discrimination of AD is based on the fact that AD subjects have significantly less tonic REM eEG energy in the 13–30 Hz frequency range and more in the 1–10 Hz range than control or depressed subjects, as shown in conventional spectral analysis.

Neural Network Model: Application to Automatic Analysis of Human Sleep

We describe an approach to automatic all-night sleep analysis based on neural network models and simulated on a digital computer. First, automatic sleep stage scoring was performed using a multilayer feedforward network. Second, supervision of the automatic decision was achieved using ambiguity rejection and artifact rejection. Then, numerical analysis of sleep was carried out using all-night spectral analysis for the background activity of the EEG and sleep pattern detectors for the transient activity. Computerized analysis of sleep recordings may be considered as an essential tool to describe the sleep process and to reflect the dynamical organization of human sleep.

Spectral power and coherence analysis of sleep EEG in AIDS patients: decrease in interhemispheric coherence.

Fifteen patients aged between 26 and 55 years with the acquired immunodeficiency syndrome (AIDS) and various cerebral manifestations of the disease underwent an all-night sleep electroencephalogram (EEG) registration. The recordings of 15 age-matched volunteers were examined as controls. Sleep stages were determined visually and the following spectral analysis was based on corresponding artifact-free 40-second periods. The sampling rate was 64 second-1, the spectral resolution was 0.25 Hz and the frequency ranged from 0.25-24 Hz. The power density spectra of eight EEG derivations (left and right frontopolar, frontal, central and occipital; reference montage to the ipsilateral Cb electrodes) and the coherence spectra of interhemispheric (interfrontal, interoccipital) and intrahemispheric (frontooccipital, left and right) channel pairs were computed. The power density of the patients in the 11.5-13-Hz frequency range of nonrapid eye movement (NREM) sleep was considerably lower than that of the controls (p < 0.05 and p < 0.01 at left and right frontal derivations, two-tailed Mann-Whitney U test). The power density of rapid eye movement (REM) sleep showed no consistent differences between the two groups. The interfrontal coherence of the whole frequency range below 12 Hz was markedly lower in the patient group. This applied to NREM sleep and also to REM sleep (p < 0.01 and p < 0.001 for different frequency bands between 1 and 12 Hz in NREM and REM sleep). Possible relations to clinical features are discussed.

Relationship of age to power spectrum analysis of EEG during sleep.

We describe a method of power spectrum analysis of all-night sleep EEGs in 20 normal subjects aged 18-43 years. The analysis calculates the energy of the whole sleep period, the various frequency bands, and selected sleep stages automatically. The numerical value of the energies was directly comparable between subjects, presented in numbers (microV2s) and displayed as a color density spectral array with fixed power values for each color. A significant relationship between age and power spectra was found, in that total energy/minute was higher in younger subjects than in older. The energy in delta sleep/minute also showed an inverse relationship with age.

Short technical note: quantification of periodic breathing: preliminary studies.

Although the apnea/hypopnea index is the most widely used measure of breathing pattern abnormality during sleep, this index gives no information about the strength of the oscillation in the breathing pattern, its periodicity or its regularity. Such information may be required in research studies involving breathing patterns and how they are affected by interventions. We are exploring spectral analytic methods to determine two normalized indices, the periodicity index and the modified modulation index, to examine periodic breathing for all-night sleep studies. These methods are automatic and require no user interaction. Data were obtained from 11 heart failure patients who slept for a total of 21 nights in the sleep laboratory. Because individual patients had a marked regularity of their Cheyne-Stokes respiration during sleep, one would expect an extremely high correlation between the traditional measures of breathing pattern abnormality and these spectral analytic techniques. Indeed we found that there was an extremely high correlation between the periodicity index and the modulation index and the traditional measures of apnea/hypopnea index and the proportion of the night with periodic breathing (p less than 0.02 in all cases). When the breathing pattern was irregular but still with many apneas there was a discrepancy between the apnea index and the indices of periodicity. These techniques are still preliminary and future studies will determine their limitations in other patient populations and where the pattern is unstable.

Quantitative analysis of the EEG during tonic REM sleep — methodology

Frequency and amplitude characteristics of the clinical (waking) electroencephalogram (EEG) can be diagnostically be limited by neuronal degenerative disorders such as Alzheimer's or other cortical dementias. However, interpretation of the clinical EEG may be limited by many factors, including movement and muscle artifacts and uncontrolled variations along the alert/drowsy continuum. Moreover, the clinical EEG involves subjective judgment by experts whose opinions often differ. In an effort to address these problems, we have developed a computer-automated technology that examines the digitized, all-night sleep EEG for frequency and amplitude characteristics of potential diagnostic relevance to Alzheimer's dementia. Robust time series analysis techniques and a modified power spectral analysis (Z-spectra) are used to suppress artifactual information and to automatically select samples of tonic REM sleep EEG. The spectra (amplitude vs. frequency relationship) of this specific EEG state is then assessed for diagnostically relevant information.

The effect of SRIF on the EEG sleep of normal men

The aim of this investigation was to evaluate EEG sleep, especially measures of delta-wave sleep, during and after the administration of somatostatin (SRIF). Eleven normal men, ages 22–37 yr, were administered saline or SRIF (0.1 μg/kg/min IV) over 160 min at bedtime. SRIF delayed sleep-related growth hormone (GH) secretion without altering the amount of GH available during the entire night of sleep. No changes in delta-wave sleep occurred during either the first 100 min of sleep or the remainder of the night. Furthermore, all major EEG sleep variables were not significantly different between the saline and SRIF infusion night. It would not appear that the peripheral administration of this dose of SRIF or the subsequent delay of GH release has quantitative effects on EEG measures of all-night sleep.

Effect of Clonidine in Obstructive Sleep Apnea

The current treatment of choice for obstructive sleep apnea is continuous positive airway pressure. However, not all patients tolerate this form of therapy. We evaluated the effect of clonidine hydrochloride, an alpha 2-adrenergic agonist with REM-suppressant activity, in eight male patients with obstructive sleep apnea. In each patient, sleep-stage distribution and breathing pattern in two all-night sleep studies performed during a 10-day course of clonidine were compared with those of two control and two placebo nights. A dose of 0.2 mg of clonidine administered orally at bedtime totally suppressed REM sleep in two patients. In the other six patients, the same dose decreased percent time spent in REM sleep from a control of 13.4 +/- 1.0 to 8.6 +/- 1.4% (mean +/- SEM, p less than 0.05). The latency to REM sleep increased in the latter group from a control of 129 +/- 9 to 308 +/- 24 min (p less than 0.001). Clonidine had no effect on the frequency and duration of non-REM breathing abnormalities. Under clonidine, the level of nocturnal hypoxemia improved in six patients. This was due to a total suppression of REM and the consequent lack of REM apneas in two patients. In four patients, upper airway obstruction disappeared during period of unsuppressed REM sleep, and SaO2 remained above 90% throughout this sleep stage. Clonidine transformed the pattern of sleep-disordered breathing during unsuppressed REM in the other two patients from that of repetitive obstructive hypopneas associated with persistent hypoxemia to occlusive apneas and cyclical hypoxemia. These results were observed consistently in all patients during both clonidine-sleep studies.(ABSTRACT TRUNCATED AT 250 WORDS)

All-night EEG sleep in drug naive patients with a first episode of schizophrenia

All-night EEG sleep in drug naive patients with a first episode of schizophrenia

The effect of noise on sleep--changes in hypnograms of subjects exposed to repeated truck-passing sound

The effect of traffic noise on sleep was evaluated in an experimental room using repeated recorded truck-passing sounds. The peak sound level was 55, 60 or 65 dB (A) with frequencies of three times per hour. The background noise of the exposure night was Leq 42 dB (A) and that of the control night was Leq 35 dB (A). The subjects were five students 23 to 24 years old. The sleep stage of each epoch with a 20-second duration was judged visually based on the criteria of Rechtschaffen & Kales and the data of the second night of noise-exposure and the control night were used. The sleep parameters used were total sleep time (TST), each sleep stage, % of sleep stage against TST, sleep efficiencies, sleep latency, REM latency, REM cycle, REM duration, waking from sleep, number of stage shifts, and subjective sleep judged by the OSA sleep inventory. A paired t test was used for the statistical analysis. TST, REM stage in minutes, and % of REM stage against TST of the exposure night were significantly decreased compared with those of the control night. Other objective and subjective parameters showed no changes during noise exposure. Dividing the all-night into halves, the amount and % of each sleep stage were compared between the exposure and control night. There was no change of sleep stage in the former half, but the % and amount of REM sleep in the latter half were significantly decreased as a result of the noise exposure. The decreases of REM sleep and % REM against TST, especially in the latter half of all-night sleep, were caused by the intermittent truck-passing sounds 20 to 30 times per night.

Elevated rectal temperature produced by all-night bright light is reversed by melatonin infusion in men

Early morning rectal body temperature is lowest when melatonin levels are highest in humans. Although pharmacological doses of melatonin are hypothermic in humans, the relationship between endogenous melatonin and temperature level has not been investigated. We measured rectal body temperature in nine normal men whose melatonin levels were suppressed by all-night sleep deprivation in bright light and compared values with those seen in sleep in the dark, sleep deprivation in dim light (to control for the stimulatory effect of wakefulness on temperature), and sleep deprivation in bright light with an infusion of exogenous melatonin that replicated endogenous levels. Minimum rectal temperature, calculated from smoothed temperature data from 2300 to 0515 h, was greater in bright-light sleep deprivation, resulting in suppression of melatonin, than in conditions of sleep deprivation in dim light or sleep in the dark. An exogenous melatonin infusion in bright light returned the minimum temperature to that seen in dim-light sleep deprivation. A nonsignificant elevation in mean and minimum temperature was noted in all conditions of sleep deprivation relative to sleep. We conclude that melatonin secretion contributes to the lowering of core body temperature seen in the early morning in humans.

Immediate effects of intravenous clomipramine on sleep and sleep-related secretion in depressed patients

An i.v. challenge dose of clomipramine (12.5 mg) was given to eight outpatients with major depression. The procedure facilitated the examination of all-night sleep and sleep-related neuroendocrine changes (cortisol, growth hormone, and prolactin). In comparison to baseline saline nights, the patients experienced a profound suppression of rapid eye movement (REM) sleep throughout the night with no rebound recovery in the second half of the night. Furthermore, REM-suppressing effects were noted on the following no-drug night. In contrast, little effect on delta wave sleep was found, except for increased consilidation of delta waves within stage 3 and 4 sleep. Delta sleep measures were significantly correlated with levels of cortisol and growth hormone.

Somnambulistic eating: A report of three cases

Somnambulism is a disorder of arousal that often includes complex, wake-like behavior with an unclear connection to conscious wishes. During episodes of somnambulism, appetitive behaviors are unusual and, when they do, occur, raise questions as to the true state of consciousness of the patient. This is the first report of somnambulistic sleepeating in which polysomnographic studies were performed to document the sleep-related nature of the nocturnal eating. During all-night sleep studies, three patients complaining of eating during sleep had episodic behavior in non-REM sleep, consistent with a somnambulistic etiology. In all three patients, a conscious preoccupation with food was present and two patients showed a high percentage of slow-wave sleep. These findings suggest a concurrence of organogenic and psychogenic factors, that has been postulated previously to underlie somnambulism in adults.

Sleep Evaluation in Chronic Insomniacs during 14-Day Use

This article contains the sleep results of the efficacy study of flurazepam 30 mg and 15 mg, midazolam 15 mg, and placebo in the 99 chronic insomniacs studied as part of this multicenter study. After a 20-day drug washout, all-night sleep was recorded on 2 baseline nights, on the first 2 treatment nights, on treatment night 7, and on the last 2 nights of the study (nights 13 and 14). To reduce the number of comparisons, electroencephalographic (EEG) sleep latency, EEG wake time, EEG sleep efficiency, post-sleep questionnaire (PSQ) sleep latency, and PSQ total sleep were preselected as the major sleep variables. Between-groups comparisons indicated that, when compared with the placebo control, all drugs improved sleep, but differences were statistically significant only for the first 2 nights, i.e., the early interval. Midazolam was more effective than either dose level of flurazepam on treatment night 1. Within-group analyses indicated that all drug groups showed significantly improved sleep from baseline throughout drug administration, but the placebo group did not significantly improve from baseline by either objective or subjective measures at any of the three time intervals. The sleep of patients taking flurazepam 30 mg did not differ significantly from the sleep of those receiving the 15 mg dose for any of the five major sleep variables at any interval. Objective EEG and subjective PSQ sleep variables showed significant positive correlations.

O83 Influence of sleep on auditory cognitive potentials. A topographic study during physiological all-night sleep

O83 Influence of sleep on auditory cognitive potentials. A topographic study during physiological all-night sleep

Sleep, Performance, and Plasma Levels in Chronic

Methods are described for a five-center study of flurazepam and midazolam, in which 107 patients with histories of benzodiazepine use for chronic insomnia were enrolled. Data were available for 99 of these patients. Staff and patient manuals and a behavior-based computer system were specially designed to measure and delineate clearly the study procedures and parameters. Patients were carefully followed and supported during a 20-day washout period and under- went extensive training on psychomotor performance tasks. They received placebo for 2 nights and were then randomly assigned to one of four study treatments—flurazepam 15 or 30 mg, midazolam 15 mg, or placebo—for 14 consecutive nights. All-night sleep electroencephalographic recordings were obtained on study nights – 1 and 0 (placebo) and 1, 2, 7, 13, and 14 (treatment nights). Results of four computer-generated psychomotor performance tasks and three cognitive tasks, plus subjective evaluations of sleep, performance, and mood, were recorded in the morning after each night spent in the sleep laboratory. Blood and urine samples were analyzed for drug concentrations in plasma and for compliance with the protocol. A pilot study, using a high (nonclinical) dose of flurazepam (45 mg), preceeded the multicenter study and was designed to evaluate tests in healthy volunteers and to familiarize staff with equipment and tests.

Predicting mortality in mixed depression and dementia using EEG sleep variables

The authors report a study of electroencephalographic (EEG) sleep predictors of two-year mortality in 26 elderly patients with mixed symptoms of depression and cognitive impairment. Patients who had died by two-year follow-up were characterized by significantly longer rapid eye movement (REM) sleep latencies at baseline, less robust REM sleep rebound following all-night sleep deprivation, and baseline apnea-hypopnea indexes greater than 3. Logistic regression analysis using the apnea-hypopnea index value and REM latency correctly predicted 77% of survivors and non-survivors. Survival time following initial measurements was significantly correlated with REM sleep time (r = 0.78, p less than .02) and duration of first REM sleep period (r = 0.75, p less than .02). The authors speculate that changes in these predictor variables may indicate impairment in the cholinergic control of cognitive function, REM sleep, and respiratory function.

Improved physical fitness failed to alter the EEG patterns of sleep in young women.

We investigated the effect of a 12-week physical training programme on the sleep of nine unfit women. Data were collected at 0, 4, 8 and 12 weeks of the training programme. Changes in fitness were assessed by changes in maximal oxygen consumption (VO2max) and onset of blood lactate turn point (LTP). Lean body mass (LBM) was calculated from total body potassium measurements. The all-night sleep recordings were made following days during which the subjects carried out their normal daily routines and did no extra exercise. Although cardiorespiratory fitness improved significantly as indicated by an increase in both VO2max and LTP, there was no change in LBM. The improvement in cardiorespiratory fitness did not result in any changes in the sleep parameters measured. Other workers have reported an improvement in sleep quality in eight army recruits during their basic training. The male recruits showed improved cardiorespiratory fitness and an increase in muscle bulk. These results suggest that increased fitness only facilitates sleep when there is an associated increase in LBM. Alternatively it may be that the response of sleep to improved fitness is sex-linked.

Effects of brief naps on mood and sleep in sleep- deprived depressed patients

To determine the effects of brief naps on mood and electroencephalographic (EEG) sleep in sleep-deprived depressed patients, data from 19 hospitalized patients with depression were analyzed; all were kept awake from 0700h until the following day, when they were allowed 10-min naps at either 0830h or 1500h. Six of the patients showed a clinically significant improvement (>40%change) on the Hamilton Rating Scale for Depression (HRSD) before the nap after all-night sleep deprivation, and the group as a whole showed a significant improvement on the HRSD, the Profile of Mood States, and the Brief Psychiatric Rating Scale subscale for depression. Naps did not alter mood in the responders, but did improve measured depression on the HRSD in the non-responders. Morning and afternoon naps did not differ significantly in their effects on mood or nap sleep. On the recovery sleep, patients who were classified as responders after the nap showed a significantly greater increase in delta (Stage 3 + 4) sleep compared with baseline than nonresponders.

Automatic real-time analysis of human sleep stages by an interval histogram method

A new interval histogram method for automatic, all-night sleep stage scoring, simulated on a digital computer, is described. The system consists of a 2-step analysis. The first step is recognition of elementary patterns in EEG, EOG and EMG, and the second step is the determination of sleep stages based on these parameters. Correlation of this method with power spectral analysis of the dominant EEG patterns during each sleep stage supported the reliability of the first step analysis. Overall agreement (89.1%) between the computer and human judges was only 3% less than the agreement (92.1%) among the scorers, indicating considerable reliability of the second step. The primary areas of disagrement that arose in the identification of sleep stages occurred with a stages 1, 2 and REM. To improve scoring accuracy, the system may require epoch sequence information. The profile of the elementary parameters of the EEG signals clearly illustrated the cyclic nature of these activities throughout the night. The alpha and delta 2 waves clearly separated the awake state from sleep stages. Beta 2 can discriminate stages 1 and REM from stage 2, and the best indicator for distincting stage 1 from REM was muscle activity. Sigma and spindles were prominent during stage 2 sleep. Both delta 2 and high voltage delta waves distinguished stage 3 from stage 4. On the other hand, delta 1 was evenly distributed and seemed to be common to all sleep stages.