Irregular circadian rhythm and cognitive impairment are frequently observed in patients with chronic schizophrenia. However, their effects in different living environments or with aging remain unclear. The aim of this study was to clarify the characteristics of circadian rhythm and cognition function in the patients with chronic schizophrenia.

This report described data collected using continuous wrist-active monitoring in real-life settings for seven days and the Brief Assessment of Cognition in Schizophrenia Japanese Version (BACS-J) from 10 inpatients with chronic schizophrenia, 10 outpatients with chronic schizophrenia, and 15 healthy elderly people. The Global Assessment of Functioning (GAF) Scale was used to measure the social functioning in the patients with chronic schizophrenia.

The outpatients with chronic schizophrenia exhibited highly interrupted circadian patterns in terms of stability and the fragmentation of activity (p < 0.05) as indexed according to Interdaily Stability (IS) and Intradaily Variability (IV). The inpatients with chronic schizophrenia indicated the most stable rhythm (p < 0.05) and inactive state (p = 0.001) among the groups. Also, the inpatients with chronic schizophrenia showed poorer cognitive functioning with Z-scores of subtests except digit sequencing (p < 0.01). According to stepwise linear regression analysis, the motor speed of BACS-J and IS of circadian parameters were the most powerful variables to predict the GAF in patients with chronic schizophrenia.

The characteristics of circadian rhythm and cognition function in the inpatients with chronic schizophrenia appear distinct from those in the outpatients and the healthy elderly people. Circadian rhythm and cognition function in the patients with chronic schizophrenia may, in part, be affected by different living environments.