Fast sleep spindle reduction in schizophrenia and healthy first-degree relatives: association with impaired cognitive function and potential intermediate phenotype
BACKGROUND Slow waves and sleep spindles, the main oscillations during non-rapid eye movement sleep, have been thought to be related to cognitive processes, and are impaired in psychotic disorders. Cognitive impairments, seen early in the course of psychotic disorders, may be related to alterations in these oscillations, but few studies have examined this relationship. METHOD Twenty seven untreated patients with a recently diagnosed psychotic disorder had polysomnographic sleep studies and neuro-cognitive testing. RESULTS Reduced power in the sigma range, which reflects spindle density, was associated with impaired attention, and reasoning, but not intelligence quotient (IQ). Slow wave sleep measures were not significantly associated with any cognitive measures. CONCLUSIONS Impairments in sleep spindles may be associated with cognitive deficits in the early course of psychotic disorders. These observations may help clarify neuro-biologic mechanisms of cognitive deficits in psychotic disorders such as schizophrenia.