Background and goals: Sleep disturbances have been noted not only during affective episodes in bipolar disorder, but also between affective episodes. The goal of this study was to assess and identify determinants of sleep quality in patients with bipolar I disorder.
Methods: This cross-sectional study enrolled patients with bipolar disorder who were currently in remission. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI). Mood symptoms were evaluated using the Young Mania Rating Scale (YMRS) and the Hamilton Depression Rating Scale (Ham-D). Adherence was assessed using the Medication Adherence Rating Scale.
Results: The mean age in the sample (N=103) was 37.4 years; 44.7% of the sample were men. On the basis of PSQI scores, 41 patients (39.8%) were poor sleepers. Poor sleepers had significantly higher Ham-D scores (mean score of 1.8 vs. 0.9, P=0.012) and higher rates of medication nonadherence (36.6% vs. 11.3%, P=0.002). The relationship between Ham-D scores and sleep quality did not remain significant when the sleep-related items on the Ham-D were removed. Logistic regression analysis suggested that medication nonadherence was the only independent predictor of poor sleep quality in this study.
Conclusions: A significant proportion of patients with bipolar disorder who are in remission have sleep problems that seem to be independent of core symptoms of depression.