The relationship between objective sleep variables and subjective sleep estimation in schizophrenia

AIM: Few investigations of sleep structure in schizophrenia have concentrated on the relationship between objective and subjective sleep variables. The aim of this study was to assess objective sleep variables and subjective estimation of sleep duration and sleep quality. METHODS: Polysomnography was performed in 20 chronic patients with schizophrenia during three consecutive nights. After final awakenings subjects answered questions concerning subjective estimations of sleep duration, sleep latency, number of awakenings, and sleep depth. Pearson correlations between ranged subjective reports and objective sleep variables were performed. RESULTS: The results showed a high positive correlation between objective sleep latency and its subjective estimation; a positive correlation between subjective estimation of sleep depth and percentage of slow wave sleep (SWS%); a positive correlation between eye movement (EM) density and subjective estimation of wakefulness during the night; and a negative correlation between EM density and dream reports. CONCLUSION: We concluded that objective sleep variables are related to subjective sleep estimation in schizophrenic patients. In these patients, EM activity in REM sleep is related to the subjective feeling of wakefulness.