Sleep spindle activity and cognitive performance in patients with schizophrenia : A systematic review

Abstract: Patients diagnosed with schizophrenia (SZ) show major deficits in cognitive functioning andsleep spindle activity. As much indicates that sleep spindle activity is related to cognitive performance, this literature review intended to investigate the degree of their relationship inpatients with SZ. The eligible criteria for the studies were that they measured sleep spindle activity and cognitive functioning in patients with SZ and included a non-clinical controlgroup. Studies with comorbid diagnoses were excluded. Searches were conducted between the 5th and 6th of March 2023 on PsycINFO, PubMed, Web of Science, and Medline databases. Seven studies met the eligibility criteria. The studies were written in English and published between 2007 and 2022. The quality of the studies was assessed using the JBICritical Appraisal Checklist for Analytical Cross-Sectional Studies. The results were synthesized by following a structured narrative and tables. The total number of participants with SZ was 141 and 149 in the non-clinical control group. The age of the participants ranged between 18 and 65 and were mainly men. Patients with SZ showed significantly reduced sleep spindle activity and cognitive performance compared to the control group. Several studies found positive correlations between cognitive performance and spindle density inboth groups. Some correlations were only significant for patients with SZ, indicating thatsleep spindle activity affects cognitive performance up to one point. A suggestion for further studies is to investigate the possibility to assess cognitive impairments in patients with SZ by inducing sleep spindle density.