Sleep quality impairments in schizophrenia and bipolar affective disorder patients continue during periods of remission: a case-controlled study

OBJECTIVE: Bipolar disorder (BD) and schizophrenia are chronic psychiatric disorders in which sleep disorders are commonly seen. In mental disorders, residual symptoms may persist even if symptoms are greatly reduced overall. The aim of this study was to compare the sleep quality of schizophrenia and BD patients in remission with that of healthy controls. METHODS: Forty-three patients with schizophrenia, 46 BD patients in remission for at least 3 months, and 51 healthy controls were included the study. The Beck Anxiety Inventory (BAI), Beck Depression Inventory (BDI), Young Mania Rating Scale (YMRS) and Pittsburgh Sleep Quality Index (PSQI) were administered to all participants and the Positive and Negative Syndrome Scale (PANSS) was administered to patients with schizophrenia. RESULTS: Poor sleep quality was more frequent in the patient groups than the control group (p=0.009). PSQI score was positively correlated with duration of disease (r=0.236; p=0.026), number of cigarettes smoked per day (r=0.430; p<0.001), body mass index (r=0.189; p=0.025), and negatively correlated with duration of remission (r=-0.224; p=0.0359). CONCLUSION: Schizophrenia and BD patients in remission had worse sleep quality than a control group. Sleep quality was worst in the patients with schizophrenia. The severity of sleep disorder symptoms was positively associated with disease duration and negatively associated with duration of remission. Schizophrenia and BD patients should be carefully evaluated for symptoms of sleep disorders even when they are in clinical remission and should be offered additional treatment for sleep disorder symptoms when necessary.