Association Between Sleep Disruption and Verbal Declarative Memory in Schizophrenia

Abstract

Schizophrenia is commonly associated with reduction in quality of sleep and a reduction in declarative memory capacity. One of the outcomes of the disease in terms of sleep quality is increased prevalence of sleep abnormalities including insomnia and poorer outcomes on EEG sleep architecture. Reduction in sleep spindle density is among the indicators of abnormalities in sleep architecture in patients with schizophrenia. In this study, the primary objective was to compare sleep spindle densities in patients with schizophrenia with the spindle densities in normal participants; as well as to compare the same variable between medicated schizophrenia patients and non-medicated schizophrenia patients. A meta-analysis of 12 studies was conducted to realize the study objective. Findings from the meta-analysis show that schizophrenia is indeed associated with sleep abnormalities as characterized by various features including reductions in sleep spindle densities. Medicated schizophrenia patients also had better outcomes in preventing sleep abnormalities than non-medicated patients. None of the studies directly examined the impacts of schizophrenia on declarative memory.