Insomnia in somatoform pain disorder: sleep laboratory studies on differences to controls and acute effects of trazodone, evaluated by the Somnolyzer 24 x 7 and the Siesta database

Periodic limb movements in sleep in patients using antidepressants

Depression and periodic limb movement disease are both common disorders which frequently co-exist. Furthermore, antidepressants are known to cause and worsen periodic limb movements in sleep, which can worsen the quality of sleep and subsequently daytime symptoms. However, the effect of antidepressants on periodic limb movements is not uniform and depends on their mechanism of action. In this review we summarise the knowledge on the mechanism of periodic limb movements in sleep, and how changes in the concentration of neurotransmitters can contribute to them. We comprehensively evaluate the literature on antidepressants induced periodic limb movement in sleep. Based on this, we suggest clinical implications and further focus on research.

Periodic leg movements during sleep associated with antidepressants: A meta-analysis

Studies explicitly reporting data concerning the evaluation of the effect of antidepressants on the periodic leg movements during sleep (PLMS) index obtained by polysomnography were reviewed and selected. A random-effects model meta-analysis was carried out. The level of evidence was also assessed for each paper. Twelve studies were included in the final meta-analysis, seven interventional and five observational. Most studies were characterized by Level III evidence (non-randomized controlled trials), with the exception of four studies, which were classified as Level IV (case series, case-control, or historically controlled studies). Selective serotonin reuptake inhibitors (SSRIs) were used in seven studies. The analysis of the assessments involving SSRIs or venlafaxine showed an overall large effect size, clearly much larger than that obtained with studies using other antidepressants. Heterogeneity was substantial. This meta-analysis confirms the previous reports on the increase in PLMS often associated with the use of SSRIs (and venlafaxine); however, the absent or smaller effect of the other categories of antidepressants needs to be confirmed by more numerous and better controlled studies.

Trazodone affects periodic leg movements and chin muscle tone during sleep less than selective serotonin reuptake inhibitor antidepressants in children

STUDY OBJECTIVES

To test the hypothesis that children taking trazodone have less leg movements during sleep (LMS) and higher rapid eye movement (REM) sleep atonia than children taking selective serotonin reuptake inhibitors (SSRIs) but more than normal controls.

METHODS

Fifteen children (9 girls and 6 boys, mean age 11.7 years, standard deviation [SD] 3.42) taking trazodone (median dosage 50 mg/d, range 25-200 mg) for insomnia and 19 children (11 girls and 8 boys, mean age 13.7 years, SD 3.07) taking SSRIs for depression, anxiety, or both were consecutively recruited, as well as an age- and sex-matched group of 25 control children (17 girls and 8 boys, mean age 13.7 years, SD 3.11). LMS were scored and a series of parameters was calculated, along with the analysis of their time structure. The Atonia Index was then computed for each non-REM sleep stage and for REM sleep.

RESULTS

Children taking trazodone exhibited slightly higher leg movement indices than controls but lower than those found in children taking SSRIs and their time structure was different. Chin electromyogram atonia in all sleep stages was not significantly altered in children taking trazodone but was decreased in children taking SSRIs, especially during non-REM sleep.

CONCLUSIONS

In children, SSRIs but not trazodone are associated with a significantly increased number of LMS, including periodic LMS, and increased chin tone in all sleep stages. The assessment of periodic limb movement disorder and REM sleep without atonia might not be accurate when children are taking SSRIs because of their significant impact.

CITATION

DelRosso LM, Mogavero MP, Bruni O, Schenck CH, Fickenscher A, Ferri R. Trazodone affects periodic leg movements and chin muscle tone during sleep less than selective serotonin reuptake inhibitor antidepressants in children. J Clin Sleep Med. 2022;18(12):2829-2836.

Automated Scoring of Sleep and Associated Events

Conventionally, sleep and associated events are scored visually by trained technologists according to the rules summarized in the American Academy of Sleep Medicine Manual. Since its first publication in 2007, the manual was continuously updated; the most recent version as of this writing was published in 2020. Human expert scoring is considered as gold standard, even though there is increasing evidence of limited interrater reliability between human scorers. Significant advances in machine learning have resulted in powerful methods for addressing complex classification problems such as automated scoring of sleep and associated events. Evidence is increasing that these autoscoring systems deliver performance comparable to manual scoring and offer several advantages to visual scoring: (1) avoidance of the rather expensive, time-consuming, and difficult visual scoring task that can be performed only by well-trained and experienced human scorers, (2) attainment of consistent scoring results, and (3) proposition of added value such as scoring in real time, sleep stage probabilities per epoch (hypnodensity), estimates of signal quality and sleep/wake-related features, identifications of periods with clinically relevant ambiguities (confidence trends), configurable sensitivity and rule settings, as well as cardiorespiratory sleep staging for home sleep apnea testing. This chapter describes the development of autoscoring systems since the first attempts in the 1970s up to the most recent solutions based on deep neural network approaches which achieve an accuracy that allows to use the autoscoring results directly for review and interpretation by a physician.

Somatic Symptoms and Sleep Disorders: A Literature Review of Their Relationship, Comorbidities and Treatment

This study aimed to investigate the relationship between somatic symptom disorder (SSD) and sleep disorders, following three research questions: (1) How are these disorders correlated? (2) What are the comorbidities reported in these patients? and (3) What are the most effective pharmacological and non-pharmacological treatments for both conditions? PubMed, Scopus, OVID, Medline, and ProQuest databases were searched for relevant articles published between 1957–2020. Search terms included “somatic symptoms disorder”, “sleep disorders”, “insomnia”, “somatoform”, “somatization”, “therapeutic”, “psychotherapy”, and alternative, formerly used terms for SSD. Forty papers were finally included in the study. Prevalence of insomnia in SSD patients ranged between 20.4–48%, with this being strongly correlated to somatic symptoms and psychosocial disability. The most relevant comorbidities were generalized anxiety disorder, depression, fatigue, negative mood, substance use, orthorexia, alexithymia, anorexia, weight loss, poor eating habits, and acute stress disorder. Patients receiving antidepressant therapy reported significant improvements in insomnia and somatic symptoms. In terms of non-pharmacological interventions, cognitive-behavioral therapy (CBT) showed improvements in sleep outcomes, while the Specialized Treatment for Severe Bodily Distress Syndromes (STreSS) may represent an additional promising option. Future research could include other medical and psychosocial variables to complete the picture of the relationship between sleep disorders and somatic symptoms.

Advanced Analysis of Pharmaco-Sleep Data in Humans

Pharmaco-sleep studies in humans aim at the description of the effects of drugs, most frequently substances that act on the central nervous system, by means of quantitative analysis of biosignals recorded in subjects during sleep. Up to 2007, the only standard for the classification of sleep macrostructure that found worldwide acceptance were the rules published in 1968 by Rechtschaffen and Kales. In May 2007, the AASM Manual for the Scoring of Sleep and Associated Events was published by the American Academy of Sleep Medicine, and concerning the classification of sleep stages, these new rules are supposed to replace those developed by Rechtschaffen and Kales. As compared to the rather low interrater reliability of manual sleep scoring, semiautomated approaches may achieve a reliability close to 1 (Cohen's kappa 0.99 for 2 semiautomated scorings as compared to 0.76 for 2 manual scorings) without any decline in validity. Depending on the aim of the pharmaco-sleep study, additional analyses concerning sleep fragmentation, sleep microstructure, sleep depth, sleep processes and local aspects of sleep should be considered. For some of these additional features, rules for visual scoring have been established, while for others automatic analysis is obligatory. Generally, for reasons of cost-effectiveness but also reliability, automatic analysis is preferable to visual analysis. However, the validity of the automatic method applied has to be proven.

Computer-Assisted Automated Scoring of Polysomnograms Using the Somnolyzer System

STUDY OBJECTIVES

Manual scoring of polysomnograms is a time-consuming and tedious process. To expedite the scoring of polysomnograms, several computerized algorithms for automated scoring have been developed. The overarching goal of this study was to determine the validity of the Somnolyzer system, an automated system for scoring polysomnograms.

DESIGN

The analysis sample comprised of 97 sleep studies. Each polysomnogram was manually scored by certified technologists from four sleep laboratories and concurrently subjected to automated scoring by the Somnolyzer system. Agreement between manual and automated scoring was examined. Sleep staging and scoring of disordered breathing events was conducted using the 2007 American Academy of Sleep Medicine criteria.

SETTING

Clinical sleep laboratories.

MEASUREMENTS AND RESULTS

A high degree of agreement was noted between manual and automated scoring of the apnea-hypopnea index (AHI). The average correlation between the manually scored AHI across the four clinical sites was 0.92 (95% confidence interval: 0.90-0.93). Similarly, the average correlation between the manual and Somnolyzer-scored AHI values was 0.93 (95% confidence interval: 0.91-0.96). Thus, interscorer correlation between the manually scored results was no different than that derived from manual and automated scoring. Substantial concordance in the arousal index, total sleep time, and sleep efficiency between manual and automated scoring was also observed. In contrast, differences were noted between manually and automated scored percentages of sleep stages N1, N2, and N3.

CONCLUSION

Automated analysis of polysomnograms using the Somnolyzer system provides results that are comparable to manual scoring for commonly used metrics in sleep medicine. Although differences exist between manual versus automated scoring for specific sleep stages, the level of agreement between manual and automated scoring is not significantly different than that between any two human scorers. In light of the burden associated with manual scoring, automated scoring platforms provide a viable complement of tools in the diagnostic armamentarium of sleep medicine.

Guidelines for the recording and evaluation of pharmaco-sleep studies in man: the International Pharmaco-EEG Society (IPEG)

The International Pharmaco-EEG Society (IPEG) presents guidelines summarising the requirements for the recording and computerised evaluation of pharmaco-sleep data in man. Over the past years, technical and data-processing methods have advanced steadily, thus enhancing data quality and expanding the palette of sleep assessment tools that can be used to investigate the activity of drugs on the central nervous system (CNS), determine the time course of effects and pharmacodynamic properties of novel therapeutics, hence enabling the study of the pharmacokinetic/pharmacodynamic relationship, and evaluate the CNS penetration or toxicity of compounds. However, despite the presence of robust guidelines on the scoring of polysomnography -recordings, a review of the literature reveals inconsistent -aspects in the operating procedures from one study to another. While this fact does not invalidate results, the lack of standardisation constitutes a regrettable shortcoming, especially in the context of drug development programmes. The present guidelines are intended to assist investigators, who are using pharmaco-sleep measures in clinical research, in an effort to provide clear and concise recommendations and thereby to standardise methodology and facilitate comparability of data across laboratories.

Performance of an automated polysomnography scoring system versus computer-assisted manual scoring

STUDY OBJECTIVES

Manual scoring of polysomnograms (PSG) is labor intensive and has considerable variance between scorers. Automation of scoring could reduce cost and improve reproducibility. The purpose of this study was to compare a new automated scoring system (YST-Limited, Winnipeg, Canada) with computer-assisted manual scoring.

DESIGN

Technical assessment.

SETTING

Five academic medical centers.

PARTICIPANTS

N/A.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Seventy PSG files were selected at University of Pennsylvania (Penn) and distributed to five US academic sleep centers. Two blinded technologists from each center scored each file. Automatic scoring was performed at Penn by a YST Limited technician using a laptop containing the software. Variables examined were sleep stages, arousals, and apnea-hypopnea index (AHI) using three methods of identifying hypopneas. Automatic scores were not edited and were compared to the average scores of the 10 technologists. Intraclass correlation coefficient (ICC) was obtained for the 70 pairs and compared to across-sites ICCs for manually scored results. ICCs for automatic versus manual scoring were > 0.8 for total sleep time, stage N2, and nonrapid eye movement arousals and > 0.9 for AHI scored by primary and secondary American Academy of Sleep Medicine criteria. ICCs for other variables were not as high but were comparable to the across-site ICCs for manually scored results.

CONCLUSION

The automatic system yielded results that were similar to those obtained by experienced technologists. Very good ICCs were obtained for many primary PSG outcome measures. This automated scoring software, particularly if supplemented with manual editing, may increase laboratory efficiency and standardize PSG scoring results within and across sleep centers.

[Psychopharmacological treatment in patients with somatoform disorders and functional body syndromes]

Somatoform disorders and functional body syndromes define a major, diagnostically heterogeneous group of patients with medically unexplained physical symptoms. Psychopharmacological approaches can be derived from the conceptualization of somatoform symptoms and syndromes within a biopsychosocial model. The survey presented focuses on randomized, double-blind and placebo-controlled studies. Antidepressants show a statistically and clinically relevant impact on many somatoform symptoms. In special reference to pain symptoms serotonergic and noradrenergic antidepressants seem to mediate a more favorable effect than selective serotonin reuptake inhibitors. For some functional body syndromes, e.g. irritable bowel syndrome and fibromyalgia, a major analgesic effect of antidepressants can be underlined as well. The empirical data for fibromyalgia, however, seem to be more convincing than for irritable bowel syndrome. Pregabalin holds an empirically well established position in the treatment of fibromyalgia. As yet there is no convincing psychopharmacological strategy for chronic fatigue syndrome. Probably due to the inherent relationships to anxiety, obsessive-compulsive and depressive disorders, both hypochondria and body dysmorphic disorder can be positively treated by serotonergic antidepressants as well.

Sodium oxybate for the treatment of fibromyalgia

INTRODUCTION

Gamma-hydroxybutyrate (GHB) is a short-chain fatty acid that is synthesized within the CNS, mostly from its parent compound gamma amino butyric acid (GABA). GHB acts as a neuromodulator/neurotransmitter to affect neuronal activity of other neurotransmitters and so, stimulate the release of growth hormone. Its sodium salt (sodium oxybate: SXB) was approved by the Food and Drug Administration (FDA) for the treatment of narcolepsy. SXB has shown to improve disrupted sleep and increase NR3 (slow-wave restorative) sleep in patients with narcolepsy. It is rapidly absorbed and has a plasma half-life of 30 - 60 min, necessitating twice-nightly dosing. Most of the observed effects of SXB result from binding to GABA-B receptors.

AREAS COVERED

Several randomized, controlled trials demonstrated significantly improved fibromyalgia (FM) symptoms with SXB. As seen in narcolepsy trials, SXB improved sleep of FM patients, increased slow-wave sleep duration as well as delta power, and reduced frequent night-time awakenings. Furthermore, FM pain and fatigue was consistently reduced with nightly SXB over time. Commonly reported adverse events included headache, nausea, dizziness and somnolence. Despite its proven efficacy, SXB did not receive FDA approval for the management of FM in 2010, mostly because of concerns about abuse.

EXPERT OPINION

Insomnia, fatigue and pain are important clinical FM symptoms that showed moderate improvements with SXB in several large, well-designed clinical trials. Because of the limited efficacy of currently available FM drugs additional treatment options are needed. In particular, drugs like SXB - which belong to a different drug class than other Food and Drug Administration (FDA)-approved FM medications such as pregabalin, duloxetine and milnacipran - would provide a much-needed addition to presently available treatment options. However, the FDA has set the bar high for future SXB re-submissions, with requirements of superior efficacy and improved risk mitigation strategies. At this time, no future FDA submission of SXB for the fibromyalgia indication is planned.

Can neuroimaging help us to understand and classify somatoform disorders? A systematic and critical review

OBJECTIVE

Debate about the nature of somatoform disorders and their current diagnostic classification has been stimulated by the anticipation of new editions of Diagnostic and Statistical Manual of Mental Disorders and International Statistical Classification of Diseases and Related Health Problems diagnostic classifications. In the current paper, we review systematically the literature on the neuroimaging of somatoform disorders and related conditions with the aim of addressing two specific questions: Is there evidence of altered neural function or structure that is specifically associated with somatoform disorders? What conclusions can we draw from these findings about the etiology of somatoform disorders?

METHODS

Studies reporting neuroimaging findings in patients with a somatoform disorder or a functional somatic syndrome (such as fibromyalgia) were found using Pubmed, PsycINFO, and EMBASE database searches. Reported structural and functional neuroimaging findings were then extracted to form a narrative review.

RESULTS

A relatively mature literature on symptoms of pain and less developed literatures on conversion and fatigue symptoms were identified. The available evidence indicates that, when compared with nonclinical groups, somatoform diagnoses are associated with increased activity of limbic regions in response to painful stimuli and a generalized decrease in gray matter density; however, methodological considerations restrict the interpretation of these findings.

CONCLUSIONS

Whereas the neuroimaging literature has provided evidence about the possible mechanisms underlying somatoform disorders, this is not yet sufficient to provide a basis for classification. By adopting a wider variety of experimental designs and a more dynamic approach to diagnosis, there is every reason to be hopeful that neuroimaging data will play a significant role in future taxonomies.

Neurocognitive functioning in women presenting with undifferentiated somatoform disorders in Oman

AIM

There is a dearth of research from non-Western populations focusing on neurocognitive functioning in patients presenting with undifferentiated somatoform disorders. The aim of the present quest is to examine the presence of cognitive impairment and other health-related parameters among attendees at psychiatric settings in Oman, an Arab/Islamic country, with a diagnosis of undifferentiated somatoform disorder.

METHOD

In order to compare the performance of patients diagnosed with undifferentiated somatoform disorder (n = 20) and normal healthy subjects (n = 18) on indices of attention and concentration, tests of executive functioning, mood, somatization and vegetative functioning were carried out.

RESULTS

The performance of patients with undifferentiated somatoform disorder differed from that of normal healthy subjects on the presently operationalized indices of working memory and executive functioning, anxiety, quality of sleep and psychosomatically expressed psychological distress.

CONCLUSION

To our knowledge, this is the first study highlighting neurocognitive functioning in patients with undifferentiated somatoform disorders from a non-Western population. This type of study has the potential of shedding light on the covariates of such a debilitating and intransigent condition as undifferentiated somatoform disorder.

The relation between sleep and pain among a non-clinical sample of young adults

Poor sleep is linked to poorer daily functioning and increased risk of psychiatric symptoms. With respect to pain, the relation is bi-directional; poor sleep exacerbates pain, while greater pain adversely affects sleep. Moreover, perception of pain is subject to cognitive-emotional processes. Surprisingly, no data are available from non-clinical samples of young adults. The aim of the present study was therefore to investigate the relation between sleep and pain as a function of quality of life and depressive symptoms in young adults. The direction of influence between sleep and pain was statistically tested with two different structural equation models (SEMs). A total of 862 participants (639 women, 223 men; mean age: 24.67; SD = 5.91) completed a series of validated self-report questionnaires assessing sleep, quality of life, depressive symptoms and cognitive-emotional elaboration of pain. Sleep, pain, quality of life, and depressive symptoms were interrelated. The first SEM suggested both a direct and an indirect influence of pain on sleep, whereas the second SEM suggested that sleep had only an indirect influence on pain. Irrespective of the SEM, the relation between sleep and cognitive-emotional elaboration of pain was mediated by quality of life and depressive symptoms. For a non-clinical sample of young adults, findings did support the bi-directional relation between poor sleep and increased cognitive-emotional elaboration of pain, though other cognitive-emotional processes such as depressive symptoms and quality of life should be taken into account.

Trazodone for the treatment of fibromyalgia: an open-label, 12-week study

Background

Despite its frequent use as a hypnotic, trazodone has not been systematically assessed in fibromyalgia patients. In the present study have we evaluated the potential effectiveness and tolerability of trazodone in the treatment of fibromyalgia.

Methods

A flexible dose of trazodone (50-300 mg/day), was administered to 66 fibromyalgia patients for 12 weeks. The primary outcome measure was the Pittsburgh Sleep Quality Index (PSQI). Secondary outcome measures included the Fibromyalgia Impact Questionnaire (FIQ), the Beck Depression Inventory (BDI), the Hospital Anxiety and Depression Scale (HADS), the Brief Pain Inventory (BPI), the Short-Form Health Survey (SF-36), and the Patients' Global Improvement Scale (PGI). Trazodone's emergent adverse reactions were recorded. Data were analyzed with repeated measures one-way ANOVA and paired Student's t test.

Results

Trazodone markedly improved sleep quality, with large effect sizes in total PSQI score as well on sleep quality, sleep duration and sleep efficiency. Significant improvement, although with moderate effect sizes, were also observed in total FIQ scores, anxiety and depression scores (both HADS and BDI), and pain interference with daily activities. Unexpectedly, the most frequent and severe side effect associated with trazodone in our sample was tachycardia, which was reported by 14 (21.2%) patients.

Conclusions

In doses higher than those usually prescribed as hypnotic, the utility of trazodone in fibromyalgia management surpasses its hypnotic activity. However, the emergence of tachycardia should be closely monitored.

Trial registration

This trial has been registered with ClinicalTrials.gov number NCT-00791739.

The FIBRO System: A Rapid Strategy for Assessment and Management of Fibromyalgia Syndrome

Fibromyalgia syndrome (FMS) is a complex disorder of widespread pain and tenderness associated with numerous other symptoms including fatigue, cognitive dysfunction, nonrestorative sleep, depression, anxiety, and stiffness. While new diagnostic criteria and previous management guidelines require quantitation of the severity of associated FMS symptoms experienced by individual patients, no system for rapid patient assessment has been made available to provide a basis for diagnosis, treatment selection and follow-up for clinicians in busy practices who have limited time. This review presents the FIBRO System, an easily remembered system for FMS symptom quantitation using the FIBRO mnemonic along with verbal questions on simple 0-10 scales to assess symptom severity (the FIBRO Problem Scale) and response to treatment (the FIBRO Change Scale) along with recommendations for pharmacologic and nonpharmacologic therapies to address individual FIBRO symptoms. This symptom-based approach can improve the care of FMS patients by providing a comprehensive, focused assessment in limited time.

A symptom-based approach to pharmacologic management of fibromyalgia

Fibromyalgia is a prevalent disorder that is characterized by widespread pain along with numerous other symptoms, including fatigue, poor sleep, mood disorders, and stiffness. Previous guidelines for the management of fibromyalgia recommended an approach that integrates pharmacologic and nonpharmacologic therapies selected according to the symptoms experienced by individual patients. However, they offered no recommendations for a system of patient assessment that would provide a basis for individualized treatment selection. We present a simple, rapid and easily remembered system for symptom quantitation and pharmacologic management of fibromyalgia that combines visual analogue scale symptom scores from a modified form of the disease-neutral Fibromyalgia Impact Questionnaire, with a review of medications that can be used to treat the individual symptoms. This symptom-based approach is amenable to caring for patients with fibromyalgia in a busy clinical practice.

High prevalence of restless legs syndrome in somatoform pain disorder

Patients with somatoform pain often complain of sleep disorders, but sleep disorders are not an integrated part of the diagnosis of this disorder. Restless legs syndrome is associated with painful symptoms and sleep disturbances. The aim of our study was to evaluate the prevalence of restless legs syndrome (RLS) in somatoform pain disorder.

METHOD

In this study 100 consecutive patients (mean age: 46.4; SD: 11.4; women: 58) diagnosed with somatoform pain disorder (SPD) were clinically investigated for the occurrence of RLS at the behavioral medicine clinic for pain outpatients in the department of psychiatry within the Medical University of Vienna. The pain parameters of SPD were assessed using a pain questionnaire and visual analogue scales (VAS). The severity of RLS was established using the questionnaire of the International Restless Legs Syndrome Study Group (IRLSSG).

RESULTS

The prevalence of restless legs syndrome found in somatoform pain disorder was 42%. Interrupted sleep was found in 83.3% in somatoform pain disorder with comorbid RLS and in 64.1% in somatoform pain disorder without RLS. Patients with continuous somatoform pain had a significant higher occurrence of RLS (Sample: 55%; with RLS: 71.4% and without RLS: 43.1%). The pain parameters increased parallel to the severity of RLS. Additionally, RLS was associated with higher psychosocial disability in family life.

CONCLUSIONS

The prevalence of RLS is high in our sample of patients with somatoform pain disorder. There seems to be a difference in pain profile between patients with and without RLS. RLS may increase the pain level and prolong pain in somatoform pain disorder. RLS should be considered when a somatoform pain disorder is diagnosed.

An E-health solution for automatic sleep classification according to Rechtschaffen and Kales: validation study of the Somnolyzer 24 x 7 utilizing the Siesta database

To date, the only standard for the classification of sleep-EEG recordings that has found worldwide acceptance are the rules published in 1968 by Rechtschaffen and Kales. Even though several attempts have been made to automate the classification process, so far no method has been published that has proven its validity in a study including a sufficiently large number of controls and patients of all adult age ranges. The present paper describes the development and optimization of an automatic classification system that is based on one central EEG channel, two EOG channels and one chin EMG channel. It adheres to the decision rules for visual scoring as closely as possible and includes a structured quality control procedure by a human expert. The final system (Somnolyzer 24 x 7) consists of a raw data quality check, a feature extraction algorithm (density and intensity of sleep/wake-related patterns such as sleep spindles, delta waves, SEMs and REMs), a feature matrix plausibility check, a classifier designed as an expert system, a rule-based smoothing procedure for the start and the end of stages REM, and finally a statistical comparison to age- and sex-matched normal healthy controls (Siesta Spot Report). The expert system considers different prior probabilities of stage changes depending on the preceding sleep stage, the occurrence of a movement arousal and the position of the epoch within the NREM/REM sleep cycles. Moreover, results obtained with and without using the chin EMG signal are combined. The Siesta polysomnographic database (590 recordings in both normal healthy subjects aged 20-95 years and patients suffering from organic or nonorganic sleep disorders) was split into two halves, which were randomly assigned to a training and a validation set, respectively. The final validation revealed an overall epoch-by-epoch agreement of 80% (Cohen's kappa: 0.72) between the Somnolyzer 24 x 7 and the human expert scoring, as compared with an inter-rater reliability of 77% (Cohen's kappa: 0.68) between two human experts scoring the same dataset. Two Somnolyzer 24 x 7 analyses (including a structured quality control by two human experts) revealed an inter-rater reliability close to 1 (Cohen's kappa: 0.991), which confirmed that the variability induced by the quality control procedure, whereby approximately 1% of the epochs (in 9.5% of the recordings) are changed, can definitely be neglected. Thus, the validation study proved the high reliability and validity of the Somnolyzer 24 x 7 and demonstrated its applicability in clinical routine and sleep studies.