Sleep Disruption in Cognitive and Occupational Functioning in Bipolar Disorder

Abstract

Bipolar Disorder is frequently associated with a number of poor outcomes including, but not limited to, a significant impairment in the ability to return to premorbid levels of occupational and psychosocial functioning, often despite the remission of mood symptoms. An extensive line of research has pointed toward deficits in cognitive functioning as playing an important role in this persistent disability, with a number of studies demonstrating the presence of numerous cognitive impairments during the inter-episode period. Also present during affective episodes as well as the inter-episode periods are reports of pervasive sleep disturbance. Sleep disturbance has been associated with the onset of manic episodes and is an oft-reported prodrome of illness onset. Despite the presence of deficits in these two domains of functioning during affective episodes as well as the inter-episode phase, there has been no evaluation of the degree to which these systems may interact to maintain such high rates of functional disability. The current study attempted to integrate these three separate lines of research to examine the role sleep disruption plays in both cognitive and occupational functioning in individuals with bipolar disorder. Seventy-two males and females with bipolar disorder in the euthymic phase (n=24), primary insomnia (n=24) or no psychological or medical diagnoses (n=24) completed a week of prospective assessment of sleep disruption via self-report and actigraphy. At the culmination of the sleep assessment period, all participants were administered a battery of neuropsychological tests of executive functioning, working memory, verbal learning, and attention. Additionally, participants completed self-reports of mood symptoms and current and lifetime occupational functioning. Results were mixed relative to hypotheses. Data supports persistent sleep disturbance among individuals with bipolar disorder when assessed via self-report, but no significant differences were observed compared to controls when assessed via actigraphy. Bipolar participants exhibited significantly poorer performance on measures of verbal learning and working memory, but no other cognitive deficits were observed relative to insomnia and control participants. Bipolar participants had a greater lifetime history of being fired compared to insomnia or control participants, and deficits in executive inhibition and switching were associated with increased lifetime firings across the sample. Sleep disturbance, either subjective or objective, failed to mediate this association. Findings are partially consistent with previous reports of persistent sleep disturbance and cognitive impairment among individuals with BD in the euthymic phase. More research should be conducted to better understand the underpinnings of functional impairment in BD.