Correlates of sleep irregularity in schizophrenia.

Circadian rhythm disruption, manifested as circadian misalignment, difficulty initiating sleep, and sleep-wake irregularity, is often left unrecognized in patients with schizophrenia. Studies have shown multiple adverse consequences of sleep irregularity, but limited data is available on schizophrenia. This is a secondary analysis of a case-control study of 66 schizophrenia patients with delayed sleep-wake phase (with or without meeting criteria for the disorder) and normal sleep-wake phase (mean age = 44.08 years; 45.45% males). Potential correlates included sleep quality, daytime sleepiness, social rhythms, chronotype, psychiatric symptoms, psychosocial functioning, metabolic index, cognitive function, and sociodemographic, lifestyle and pharmacological factors. Square successive difference (SSD) scores, derived from 1-week sleep diary and actigraphy, were indexes of sleep irregularity. Multilevel modeling analysis, with SSD scores as level-1 measures and the hypothesized correlates as level-2 measures, was performed. Statistical significance was Bonferroni-adjusted. Higher SSD scores of sleep diary and actigraphy variables were significantly associated with positive and depressive symptoms, poor sleep quality, daytime sleepiness, irregular social rhythm, evening chronotype, delayed sleep-wake phase disorder, later caffeine use and dinner time, greater cigarette use, and lower dosages of hypnotics and antipsychotics. Our findings highlight the implications of sleep irregularity in schizophrenia and the need for a multimodal intervention.