Elsevier

Schizophrenia Research

Volume 82, Issues 2–3, 28 February 2006, Pages 251-260
Schizophrenia Research

Clinical significance of sleep EEG abnormalities in chronic schizophrenia

https://doi.org/10.1016/j.schres.2005.10.021Get rights and content

Abstract

This study aimed to investigate the relationship between measures of clinical symptom severity and sleep EEG parameters in a relatively diagnostically homogeneous group of patients with schizophrenia. We obtained sleep EEG data in 15 drug-free inpatients who met DSM-IV-R criteria for schizophrenia, undifferentiated type, with 15 age- and sex-matched normal controls over two consecutive night polysomnographic recordings. Clinical symptoms were assessed by the Positive and Negative Symptom Scale (PANSS) and Hamilton Rating Scale for Depression. Characteristic features of sleep disturbance were seen in patients with schizophrenia: profound difficulties in sleep initiation and maintenance, poor sleep efficiency, a slow wave sleep (SWS) deficit, and an increased REM density. SWS was inversely correlated with cognitive symptoms. REM density was inversely correlated with positive, cognitive, and emotional discomfort symptoms as well as PANSS total score. Our data demonstrate that drug-free patients with chronic undifferentiated type schizophrenia suffer from profound disturbances in sleep continuity and sleep architecture. Both the SWS deficit and cognitive impairment found in schizophrenics in this study may relate to similar underlying structural brain abnormalities.

Introduction

Sleep EEG research in schizophrenia during the past several decades has focused on the relationship between sleep parameters and underlying clinical symptoms. Schizophrenia is associated with a number of sleep EEG abnormalities, including difficulty in sleep initiation and maintenance (Tandon et al., 1992, Hudson et al., 1993, Lauer et al., 1997, Keshavan et al., 1998), decreased total sleep time (Tandon et al., 1992, Keshavan et al., 1998), poor sleep efficiency (Tandon et al., 1992, Lauer et al., 1997, Keshavan et al., 1998), a slow wave sleep (SWS) deficit (Hiatt et al., 1985, Ganguli et al., 1987, Keshavan et al., 1998, Poulin et al., 2003), and shortened REM latency (Hiatt et al., 1985, Tandon et al., 1992, Hudson et al., 1993, Poulin et al., 2003). Not all studies, however, have shown consistent findings. Such disparities may relate to differences in sample size, demographic features, phase of illness, type of treatment being received at the time of study (drug-naive vs. drug-free, drug-free duration), and diagnostic criteria for schizophrenia, as well as the definition of sleep parameters. Discrepant findings may also relate to the underlying pathophysiological and phenotypic heterogeneity of schizophrenia. Therefore, an investigation of sleep EEG in a homogeneous schizophrenia sample with control for additional confounding factors, would be of value.

Sleep EEG abnormalities in schizophrenia may provide insight into the anatomical and/or neurophysiological pathophysiology of schizophrenia. For instance, particular sleep variables provide the bridge between clinical dimensions of schizophrenia and their underlying biological basis. There is little consensus regarding the relationship of sleep abnormalities to clinical symptoms of schizophrenia (Ganguli et al., 1987, Van Kammen et al., 1988, Tandon et al., 1989, Tandon et al., 1992, Keshavan et al., 1995, Lauer et al., 1997, Zarcone and Benson, 1997). Although some studies suggested that a SWS deficit (Ganguli et al., 1987, Van Kammen et al., 1988, Tandon et al., 1989) or a decrease in REM latency (Tandon et al., 1989) was correlated with negative symptoms, others reported that total delta count (a marker of SWS) was negatively associated with positive symptoms (Keshavan et al., 1995). Other investigators failed to find any such relationships (Lauer et al., 1997).

Comprehensive models of schizophrenia have increasingly included symptoms of cognitive impairment as a distinctive feature of this disorder, independent of positive and negative symptoms (Bell et al., 1994, Lançon et al., 2000). Bell et al. (1994) performed a factor analysis of the Positive and Negative Syndrome Scale (PANSS, Kay et al., 1987) in patients with schizophrenia or schizoaffective disorder and found 5 symptom clusters: positive, negative, cognitive, hostility, and emotional discomfort. Several factor analytic studies have supported this model (Lançon et al., 2000). To our knowledge, there is no study examining the relationship between cognitive symptoms derived from PANSS and sleep parameters.

The present study was designed to investigate the relationship between measures of clinical symptom severity, in particular cognitive symptoms, and sleep EEG parameters in a relatively diagnostically homogeneous group of patients with schizophrenia.

Section snippets

Subjects

The subjects were recruited from a long-term facility of a regional metropolitan hospital according to their free will. They were given an explanation of the study processes and it was explained that they were allowed to discontinue study participation freely anytime they wanted and further, that the withdrawal from study would not affect any aspect of their treatment or hospital life. All patients were withdrawn from their routine medication solely for this study. Twenty-two patients were

Results

No significant differences between groups were observed for respiratory indices. Mean apnea-hypopnea index was 2.0 ± 2.0 (range 0.4–5.9) for patients and 2.4 ± 1.8 (range 0.5–5.5) for normal controls. Mean lowest arterial oxygen saturation was 87.7 ± 2.1% (range 83.0–91.0) for patients and 88.9 ± 2.1% (range 84.0–92.0) for normal controls. Periodic leg movement of sleep index was 0.5 ± 1.1 (range 0–4.3) for patients and 0.3 ± 0.4 (range 0–1.2) for normal controls (p > 0.1).

Discussion

Our data showed the characteristic features of sleep disturbance seen in many studies of patients with schizophrenia. As a group, patients had profound difficulties in sleep initiation and maintenance, reduced SWS, and an increased REM density. We found that SWS and REM density were both inversely correlated with clinical symptoms. Our data are the first to establish a relationship between specific sleep abnormalities (reduced SWS and reduced REM density) and cognitive deficits extracted from

References (45)

  • C.J. Lauer et al.

    From early to late adulthood: changes in EEG sleep of depressed patients and healthy volunteers

    Biol. Psychiatry

    (1991)
  • C.J. Lauer et al.

    Sleep in schizophrenia: a polysomnographic study on drug-naive patients

    Neuropsychopharmacology

    (1997)
  • J. Poulin et al.

    Sleep architecture and its clinical correlates in first episode and neuroleptic-naive patients with schizophrenia

    Schizophr. Res.

    (2003)
  • V.S. Rotenberg et al.

    Sleep structure in positive and negative schizophrenia

    Biol. Psychiatry

    (1997)
  • T. Sharma et al.

    Cognitive function in schizophrenia. Deficits, functional consequences, and future treatment

    Psychiatr. Clin. North Am.

    (2003)
  • R. Tandon et al.

    Association between abnormal REM sleep and negative symptoms in schizophrenia

    Psychiatry Res.

    (1989)
  • S.F. Taylor et al.

    Sleep onset REM periods in schizophrenic patients

    Biol. Psychiatry

    (1991)
  • A.H.C. Wong et al.

    Schizophrenia: from phenomenology to neurobiology

    Neurosci. Biobehav. Rev.

    (2003)
  • V.P. Zarcone et al.

    BPRS symptom factors and sleep variables in schizophrenia

    Psychiatry Res.

    (1997)
  • American Psychological Association
  • American Sleep Disorders Association, 1997. The International Classification of Sleep Disorders—Revised: Diagnostic and...
  • K.L. Benson et al.

    Rapid eye movement sleep eye movements in schizophrenia and depression

    Arch. Gen. Psychiatry

    (1993)
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