Clinical significance of sleep EEG abnormalities in chronic schizophrenia
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.
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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)
- et al.
Structural neural networks subserving oculomotor function in first-episole schizophrenia
Biol. Psychiatry
(2004) - et al.
Concurrent validity of the cognitive component of schizophrenia: relationship of PANSS scores to neuropsychological assessment
Psychiatry Res.
(1994) - et al.
Slow wave sleep and computed tomographic measures of brain morphology in schizophrenia
Psychiatry Res.
(1996) - et al.
Working memory functioning in schizophrenia patients and their first-degree relatives: cognitive functioning shedding light on etiology
Neuropsychologia
(2005) - et al.
Further observations on electrophysiological sleep patterns in schizophrenia
Compr. Psychiatry
(1965) - et al.
Impairment of visuospatial memory is associated with decreased slow wave sleep in schizophrenia
J. Psychiatr. Res.
(2004) - et al.
Polysomnographic characteristics of schizophrenia in comparison with mania and depression
Biol. Psychiatry
(1993) - et al.
Slow-wave sleep and symptomatology in schizophrenia and related psychotic disorders
J. Psychiatry Res.
(1995) - et al.
A longitudinal study of EEG sleep in schizophrenia
Psychiatry Res.
(1996) - et al.
Stability of the five-factor structure of the Positive and Negative Syndrome Scale (PANSS)
Schizophr. Res.
(2000)
From early to late adulthood: changes in EEG sleep of depressed patients and healthy volunteers
Biol. Psychiatry
Sleep in schizophrenia: a polysomnographic study on drug-naive patients
Neuropsychopharmacology
Sleep architecture and its clinical correlates in first episode and neuroleptic-naive patients with schizophrenia
Schizophr. Res.
Sleep structure in positive and negative schizophrenia
Biol. Psychiatry
Cognitive function in schizophrenia. Deficits, functional consequences, and future treatment
Psychiatr. Clin. North Am.
Association between abnormal REM sleep and negative symptoms in schizophrenia
Psychiatry Res.
Sleep onset REM periods in schizophrenic patients
Biol. Psychiatry
Schizophrenia: from phenomenology to neurobiology
Neurosci. Biobehav. Rev.
BPRS symptom factors and sleep variables in schizophrenia
Psychiatry Res.
Rapid eye movement sleep eye movements in schizophrenia and depression
Arch. Gen. Psychiatry
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