Sleep In Healthy Individuals Research Articles

0764 REFERENCE DATA FOR POLYSOMNOGRAPHIC AND SUBJECTIVE SLEEP IN HEALTHY ADULTS

Reference data for sleep in healthy individuals are needed for the interpretation of polysomnography and subjective sleep parameters. The aim of this analysis was to provide polysomnographic and subjective reference data for two consecutive nights based on a large sample of healthy adults. The sample was selected from the archival database of the Sleep Center at the Clinic for Psychiatry and Psychotherapy, Medical Center - University of Freiburg, and consisted of 239 healthy adults aged 19 to 83 years, including 103 males and 136 females, who were divided into five age groups. Means, standard deviations and percentiles are provided for PSG-derived sleep onset latency, total sleep time, sleep efficiency, wake time after sleep onset, REM latency, number of wake periods, percentages of time spent in different sleep stages, and arousal index for the first and second night. Periodic limb movement index and apnea hypopnea index are provided for the first night. In addition, means and standard deviations for the subjective estimation of sleep onset latency, total sleep time, sleep efficiency, wake time after sleep onset and sleep quality are provided for the same two nights. Potentials and limitations of the usage of reference data in sleep research and sleep medicine are discussed. We conclude that the informative value of sleep reference data in healthy individuals is limited due to high interindividual and intraindividual variation within sleep variables and lack of research into potential consequences of deviations from the normal range. none.

Sleep in the Acute Phase of Severe Traumatic Brain Injury

Background and Objectives. The onset of pervasive sleep-wake disturbances associated with traumatic brain injury (TBI) is poorly understood. This study aimed to (a) determine the feasibility of using polysomnography in patients in the acute, hospitalized stage of severe TBI and (b) explore sleep quality and sleep architecture during this stage of recovery, compared to patients with other traumatic injuries. Methods. A cross-sectional case-control design was used. We examined the sleep of 7 patients with severe TBI (17-47 years; 20.3 ± 15.0 days postinjury) and 6 patients with orthopedic and/or spinal cord injuries (OSCI; 19-58 years; 16.9 ± 4.9 days postinjury). One night of ambulatory polysomnography was performed at bedside. Results. Compared to OSCI patients, TBI patients showed a significantly longer duration of nocturnal sleep and earlier nighttime sleep onset. Sleep efficiency was low and comparable in both groups. All sleep stages were observed in both groups with normal proportions according to age. Conclusion. Patients in the acute stage of severe TBI exhibit increased sleep duration and earlier sleep onset, suggesting that the injured brain enhances sleep need and/or decreases the ability to maintain wakefulness. As poor sleep efficiency could compromise brain recovery, further studies should investigate whether strategies known to optimize sleep in healthy individuals are efficacious in acute TBI. While there are several inherent challenges, polysomnography is a useful means of examining sleep in the early stage of recovery in patients with severe TBI.

Disturbed sleep as risk factor for the subsequent onset of bipolar disorder – Data from a 10-year prospective-longitudinal study among adolescents and young adults

There is ample data suggesting that individuals with bipolar disorder more frequently suffer from disturbed sleep even when euthymic. Since sleep is a process that is crucial for affective homeostasis, disturbed sleep in healthy individuals may be a risk factor for the subsequent onset of bipolar disorder. Utilizing data from a large cohort of adolescents and young adults, this study tests the hypothesis that disturbed sleep constitutes a risk factor for the later onset of bipolar disorder. A representative community sample of N = 3021 adolescents and young adults (baseline age 14–24) was assessed using the standardized Composite International Diagnostic Interview and followed-up prospectively up to 3 times over up to 10 years. Disturbed sleep at baseline was quantified utilizing the corresponding items from the self-report inventory SCL-90-R. The compound value (insomnia-score) as an ordinal parameter for the severity of sleep disturbances was used to assess associations with the incidence of bipolar disorder among participants free of major mental disorder at baseline (N = 1943) using odds ratios (OR) from logistic regressions. Analyses were adjusted for age, gender, parental mood disorder and lifetime alcohol or cannabis dependence. Poor sleep quality significantly increased the risk for the subsequent development of bipolar disorder (OR = 1.75; p = 0.001). Regarding individual sleep items, trouble falling asleep and early morning awakening were predictive for the subsequent onset of bipolar disorder.Disturbed sleep in persons otherwise free of major mental disorders appears to confer an increased risk for the subsequent onset of bipolar disorder.

Studying the effects of thalamic interneurons in a thalamocortical neural mass model

Neural mass models of the thalamocortical circuitry are often used to mimic brain activity during sleep and wakefulness as observed in scalp electroencephalogram (EEG) signals [1]. It is understood that alpha rhythms (8-13 Hz) dominate the EEG power-spectra in the resting-state [2] as well as the period immediately before sleep [3]. Literature review shows that the thalamic interneurons (IN) are often ignored in thalamocortical population models; the emphasis is on the connections between the thalamo cortical relay (TCR) and the thalamic reticular nucleus (TRN). In this work, we look into the effects of the IN cell population on the behaviour of an existing thalamocortical model containing the TCR and TRN cell populations [4]. A schematic of the extended model used in this work is shown in Fig.1. The model equations are solved in Matlab using the Runge-Kutta method of the 4th/5th order. The model shows high sensitivity to the forward and reverse rates of reactions during synaptic transmission as well as on the membrane conductance of the cell populations. The input to the model is a white noise signal simulating conditions of resting state with eyes closed, a condition well known to be associated with dominant alpha band oscillations in EEG e.g. [5]. Thus, the model parameters are calibrated to obtain a set of basal parameter values when the model oscillates with a dominant frequency within the alpha band. The time series plots and the power spectra of the model output are compared with those when the IN cell population is disconnected from the circuit (by setting the inhibitory connectivity parameter from the IN to the TCR to zero). We observe (Fig. 2 inset) a significant difference in time series output of the TRN cell population with and without the IN cell population in the model; this in spite of the IN having no direct connectivity to and from the TRN cell population (Fig. 1). A comparison of the power spectra behaviour of the model output within the delta (1-3.5Hz), theta (3.75-7.5Hz), alpha (7.75-13.5Hz) and beta (13.75-30.5Hz) bands is shown in Fig. 2. Disconnecting the IN cell population shows a significant drop in the alpha band power and the dominant frequency of oscillation now lies within the theta band. An overall ‘slowing’ (left-side shift) of the power spectra is observed with an increase within the delta and theta bands and a decrease in the alpha and beta bands. Such a slowing of EEG is a signature of slow wave sleep in healthy individuals, and this suggests that the IN cell population may be centrally involved in the phase transition to slow wave sleep [6]. It is also characteristic of the waking EEG in Alzheimer’s disease, and may help us to understand the role of the IN cell population in modulating TCR and TRN cell behaviour in pathological brain conditions.

Assessment of SOMNOwatch plus EEG for sleep monitoring in healthy individuals

Polysomnography (PSG) is still the standard in sleep monitoring, with several alternative solutions developed, including simplified electroencephalographic recorders such as SOMNOwatch plus EEG. In this study, we aimed to evaluate the validity of the recordings and of the analysis of the proprietary software of this solution, compared to PSG and semiautomatic scoring, respectively. From thirteen healthy adults, we recorded 27 nights simultaneously with a classical EEG amplifier (NeuroScan system) and the ambulatory SOMNOwatch plus EEG. Thereafter, we performed (semi-) automatic sleep analysis in Somnolyzer 24x7 and DOMINO Light (SOMNOwatch software). AASM scoring sensitivity of SOMNOwatch plus EEG, as revealed by Somnolyzer 24x7, was 97.79%, and specificity 87.19%. Paired T tests revealed no significant differences between the recordings of the two EEG systems, with intraclass correlation coefficients ranging from moderate to very good. When data were analyzed in DOMINO Light, sensitivity was 92.99% and specificity was 80.90%. Our data suggest that SOMNOwatch plus EEG might serve as a reliable instrument for recording sleep in healthy individuals, but its proprietary software, DOMINO Light, still seems to have weaknesses in terms of automatic sleep staging.

Sleep respiratory disturbances and arousals at moderate altitude have overlapping electroencephalogram spectral signatures

An ascent to altitude has been shown to result in more central apneas and a shift towards lighter sleep in healthy individuals. This study employs spectral analysis to investigate the impact of respiratory disturbances (central/obstructive apnea and hypopnea or periodic breathing) at moderate altitude on the sleep electroencephalogram (EEG) and to compare EEG changes resulting from respiratory disturbances and arousals. Data were collected from 51 healthy male subjects who spent 1 night at moderate altitude (2590 m). Power density spectra of Stage 2 sleep were calculated in a subset (20) of these participants with sufficient artefact-free data for (a) epochs with respiratory events without an accompanying arousal, (b) epochs containing an arousal and (c) epochs of undisturbed Stage 2 sleep containing neither arousal nor respiratory events. Both arousals and respiratory disturbances resulted in reduced power in the delta, theta and spindle frequency range and increased beta power compared to undisturbed sleep. The similarity of the EEG changes resulting from altitude-induced respiratory disturbances and arousals indicates that central apneas are associated with micro-arousals, not apparent by visual inspection of the EEG. Our findings may have implications for sleep in patients and mountain tourists with central apneas and suggest that respiratory disturbances not accompanied by an arousal may, none the less, impact sleep quality and impair recuperative processes associated with sleep more than previously believed.

Association of sleep related events and arousals during light sleep in healthy individuals

Background: Few studies have assessed impact of sleep related physiological events on arousals.

Association of sleep related events and arousals during light sleep in healthy individuals

Association of sleep related events and arousals during light sleep in healthy individuals

Relation of sleep related events and spontaneous arousals during slow wave & REM sleep in healthy individuals

Relation of sleep related events and spontaneous arousals during slow wave & REM sleep in healthy individuals

Sleep in Women

The timing and continuity of sleep in healthy individuals is regulated by the synchronous function of the sleep homeostasis and the endogenous circadian rhythms. Multiple factors affect these two processes and the way they interact. Sleep disorders may manifest differently in men and women and these differences are particularly notable during pregnancy, lactation, and menopause. Insomnia may occur relatively commonly during pregnancy and in the postpartum, and may be the result of either a primary sleep disorder, such as obstructive sleep apnea (OSA), movement disorders such as restless legs syndrome (RLS), or sometimes depression, especially in the postpartum period. Obstructive sleep apnea may contribute to a higher risk of hypertension during pregnancy and doubles the risk for preeclampsia and preterm birth. Snoring, a frequent symptom of OSA, increases in frequency during pregnancy. Restless legs syndrome is more common in pregnant women, is more frequent in the third trimester of pregnancy, and tends to improve dramatically after delivery. Factors associated with increased RLS in pregnancy may be related to iron and folate metabolism. Risk for OSA increases after menopause and presentation with insomnia can delay the diagnosis of OSA. Various treatment options for sleep disorders in women are discussed.

Polysomnographic respiratory abnormalities in asymptomatic individuals.

Polysomnographic respiratory abnormalities have been extensively studied in the general population, but studies have not targeted completely healthy individuals. We aimed to (1) define the frequency of respiratory disturbances (RDI: events per hour of sleep) during sleep in healthy individuals using current techniques and criteria and (2) determine how these abnormalities change with age and sex. Cross-sectional analyses of RDI in healthy volunteers. One hundred sixty-three individuals (106 men) were screened for chronic medical illness, as confirmed by extensive questionnaires, physical examination, electrocardiography, and laboratory analysis. Obese subjects (body mass index > 30 kg/m2) and subjects taking medications were excluded. INTERVENTIONS, MEASUREMENTS AND RESULTS: Subjects underwent full polysomnography using current standard recording and scoring techniques. There was a remarkable increase in RDI with age, particularly over 50 years. Ninety-five percent of currently healthy subjects under 50 years of age had an RDI <15, whereas 50% of subjects older than 65 years had an RDI <15. Men had a higher RDI (median 10) than women (median 5). The effect of age on RDI was similar in men and women. RDI increases with age even in healthy individuals without symptoms or signs of obstructive sleep apnea syndrome. We do not know whether these individuals will develop pathophysiologic consequences over time or whether this increase with age reflects a normal aging process. If the former, treatment should be considered regardless of symptoms. If the latter, the criteria for treatment should be adjusted by age.

Inflammation and sleep in healthy individuals.

Inflammation is relatively common in individuals with a sleep disorder and is associated with quality of sleep. The purpose of this study was to examine whether inflammation is associated with quality of sleep in healthy individuals. Observational study in a General Clinical Research Center. This study characterized inflammation and polysomno-graphically verified sleep in 124 African American and Caucasian American women and men without a sleep disorder. Circulating levels of 3 markers and/or mediators of inflammation known to be elevated in sleep disorders and in cardiovascular disease were determined (interleukin-6 [IL-6] endothelin-1 [ET-1], soluble intercellular adhesion molecule-1 [sICAM-1]). Sleep was characterized by polysomnography. Multiple linear regression analyses showed that increasing age, male sex, and African American ethnicity were independently associated with poorer sleep. After controlling for these variables, higher levels of ET-1 were independently associated with greater sleep latency (P < or = 0.01), greater rapid eye movement (REM) latency (P < or = 0.01), more slow wave sleep (P < or = 0.05), and less stage 1 sleep (P < or = 0.01). Higher IL-6 levels were independently associated with greater REM latency (P < or = 0.05). The findings suggest that, in individuals without a known sleep disorder, ET-1, a potent vasoconstrictor and mediator of inflammation, is associated with more deep sleep, whereas both ET-1 and IL-6 are associated with increased latency of sleep and of REM. The findings underscore the complex relationships between peripheral markers of inflammation and sleep.

The Visual Scoring of Sleep in Adults

The 1968 Rechtschaffen and Kales (R & K) sleep scoring manual was published 15 years after REM sleep was discovered. Advances in the ensuing 28 years warranted a re-look at visual scoring of sleep stages. This paper describes the work of the AASM Visual Scoring Task Force, including methodology, a literature review and the rationale behind the new rules. Reliability studies of R & K scoring were reviewed; reliability was low for stage one and moderate for slow wave sleep. Evidence indicated that K complexes and slow waves are expressed maximal frontally, spindles centrally and alpha rhythm over the occipital region. Three derivations of EEG, two of electro-oculography, and one of chin EMG were recommended. Scoring by 30-second epochs was retained. New terminology for sleep stages was proposed. Attenuation of alpha rhythm was determined to be the most valid electrophysiological marker of sleep onset. Alternative measures were proposed for non-alpha generating subjects. K complexes associated with arousals were determined to be insufficient alone to define the new stage N2. No evidence was found to justify dividing slow wave sleep into two stages. No reasons were found to alter the current slow wave amplitude criteria at any age. The phenomena of REM sleep were defined. The rules for defining onset and termination of REM sleep periods were simplified. Movement time was eliminated and major body movements defined. Studies are needed to test the reliability of the new rules. Future advances in technology may require modification of these rules with time.

Hypnotic Activity of Melatonin

To establish the effect of melatonin upon nocturnal and evening sleep. Experiment I: The effect of melatonin (0.1, 0.5, 1.0, 5.0, and 10 mg), ingested at 23:30, was studied on nocturnal sleep (23:30-07:30) and core body temperature in 8 healthy volunteers. Performance was measured 8.5 h post-ingestion. On completion of the experiment dim light melatonin onsets (DLMO) were determined. Experiment II: The effect of melatonin (0.5, 1.0, 5.0, and 10 mg), ingested at 18:00, was studied on evening sleep (18:00-24:00) and core body temperature in 6 healthy volunteers. Performance was measured 6.5 h post-ingestion. Each experiment was placebo-controlled and double-blind with a cross-over design with temazepam (20 mg) as an active control. Experiment I: Melatonin (5 mg) reduced the duration of stage 3 in the first 100 min of sleep. Melatonin (0.1 mg) reduced body temperature 6.5 to 7 h post-ingestion. Temazepam increased stage 2, reduced wakefulness and stage 1, and increased the latency to REM sleep. Temazepam reduced body temperature 4.5 to 6.5 h post-ingestion. There were no changes in performance compared with placebo. DLMO occurred between 20:40 and 23:15. Experiment II: Melatonin (all doses) increased total sleep time (TST), sleep efficiency index (SEI) and stage 2, and reduced wakefulness. Temazepam increased TST, SEI, stage 2 and slow-wave sleep, and reduced wakefulness. There were no changes in body temperature or performance compared with placebo. Melatonin given at 23:30 has no significant clinical effect on nocturnal sleep in healthy individuals. Hypnotic activity of melatonin when given in the early evening (presumably in the absence of endogenous melatonin) is similar to 20 mg temazepam.