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Sleep-EEG in patients with schizophrenia: Analysis of power spectra and dimensional complexity
Increased sleep onset latency and sleep disruption have been described unanimously, decreased slow wave sleep (SWS) is controversial in patients with schizophrenia (1,2). Reductions in delta and theta power in NREM sleep (2) and, by analysis of dimensional complexity, reduced dimensionality in stage 2 and REM sleep also have been described (3). Missing studies applying both methods in the same subjects, we investigated power spectra and dimensional complexity in patients with schizophrenia (n=17, age range 22 to 44 years, medicated with amisulpride) and in matched healthy controls. We confirmed a decrease in delta power in stage 2 and SWS and a decrease in theta power in SWS. By analysis of dimensional complexity, we confirmed the reduction of dimensionality in stage 2 sleep, but did not find the reduction in REM sleep. These results support the hypothesis that in schizophrenia there is not only a modulation of quantitative classic sleep variables but also a qualitative change within these sleep stages. Our data suggest that particularly in NREM sleep the reduction in slow waves is associated with decreased modulation of activity stages. This night be relevant for functions such as memory consolidation (see abstract on memory and sleep by same first author).
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