Background Irregular sleepa€“wake cycles and cognitive impairment are frequently observed in schizophrenia, however, how they interact remains unclear. Aims To investigate the repercussions of circadian rhythm characteristics on cognitive performance and psychopathology in individuals with schizophrenia. Method Fourteen middle-aged individuals diagnosed with schizophrenia underwent continuous wrist actimetry monitoring in real-life settings for 3 weeks, and collected saliva samples to determine the onset of endogenous melatonin secretion as a circadian phase marker. Moreover, participants underwent multiple neuropsychological testing and clinical assessments throughout the study period. Results Sleepa€“wake cycles in individuals with schizophrenia ranged from well entrained to highly disturbed rhythms with fragmented sleep epochs, together with delayed melatonin onsets and higher levels of daytime sleepiness. Participants with a normal resta€“activity cycle (objectively determined by high relative amplitude of dayight activity) performed significantly better in frontal lobe function tasks. Stepwise regression analysis revealed that relative amplitude and age represented the best predictors for cognitive performance (Stroop coloura€“word interference task, Trail Making Test A and B, semantic verbal fluency task), whereas psychopathology (Positive and Negative Syndrome Scale) did not significantly correlate with either cognitive performance levels or the quality of sleepa€“wake cycles. Conclusions Consolidated circadian rhythms and sleep may be a prerequisite for adequate cognitive functioning in individuals with schizophrenia.
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机译：背景精神分裂症中经常观察到不规则的睡眠，唤醒周期和认知障碍，但是，它们如何相互作用尚不清楚。目的探讨昼夜节律特征对精神分裂症患者认知能力和心理病理学的影响。方法对十四名被诊断为精神分裂症的中年人在现实生活中进行连续腕部肌电监测，持续3周，并收集唾液样本以确定内源性褪黑激素分泌的开始作为昼夜节律标志。此外，在整个研究期间，参与者都接受了多种神经心理学测试和临床评估。结果精神分裂症患者的睡眠觉醒周期从良好的发作到高度不安的节律，睡眠时期不连续，褪黑素发作延迟，白天嗜睡程度更高。具有正常恢复活动周期（客观上由白天/晚上活动的相对幅度较高决定）的参与者在额叶功能任务中的表现要好得多。逐步回归分析显示，相对振幅和年龄是认知表现的最佳预测指标（Stroop coloura，单词干扰任务，Trail Making Test A和B，语义口语流利度任务），而心理病理学（正负综合症量表）则无明显意义与认知能力水平或睡眠质量有关。结论巩固的昼夜节律和睡眠可能是精神分裂症患者充分认知功能的前提。
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