Sleep-wake disturbance in people with interepisode bipolar disorder

Abstract

Over the past decade, researchers have shifted focus from the manic and depressive episodes to the interepisode period in the study of sleep-wake disturbance in bipolar disorder. The thesis consists of two studies: a systematic review and meta-analysis and a cross-sectional study.

The first study aimed to compile and synthesize studies that employed sleep diary, actigraphy, polysomnography, and questionnaires to compare sleep-wake patterns in people with interepisode bipolar disorder or high-risk individuals vs. normal controls and/or people with primary insomnia. Key databases were searched until June 2013. The search identified 21 eligible studies, yielding 24 sleep-wake variables. A total of 531 people with interepisode bipolar disorder, 157 high-risk individuals, 678 normal controls and 67 adults with primary insomnia were evaluated. Using a random-effects model, the analyses suggest that adults with interepisode bipolar disorder appear worse than normal controls in most variables and comparable to adults with primary insomnia in certain aspects. Sleep onset latency, wake after sleep onset, and variability of sleep-wake variables were most consistently impaired in interepisode bipolar disorder. In comparison with controls, high-risk individuals were found to have higher variability in sleep efficiency and lower relative amplitude. The findings provide a foundation for the search for candidate endophenotypes and the development of novel interventions for bipolar disorder.

The second study aimed to examine the correlates of eveningness. Ninety-eight adults diagnosed with bipolar disorder type I, II, or not otherwise specified were recruited from a regional outpatient psychiatric clinic. Participants who were interepisode completed measures of morningness-eveningness, sleep-wake disturbance, eating disturbance, quality of life, functioning, and dysfunctional sleep-related cognitions and behaviors. Linear regression analyses suggested that eveningness was associated with increased sleep onset latency, excessive daytime sleepiness, greater eating disturbance, worse physical and environmental quality of life, impaired interpersonal relationships, stronger beliefs regarding negative consequences of poor sleep, higher levels of worry or helplessness about sleep, poorer eating or drinking habits prior to sleep, adverse sleep environment and improper sleep scheduling and timing, after controlling for age, gender and years of education. The results suggest that eveningness may be an under-recognized contributor to poor outcomes in bipolar disorder. Targeted interventions on dysfunctional sleep-related cognitions and behaviors may help to reverse eveningness.