Targeting Circadian and Cognitive Dysfunction in Bipolar Disorder With Modafinil

Changes in the sleep-wake cycle are other circadian rhythms represent core features of Bipolar Disorder (BD), with sleep abnormalities in approximately 90% of patients during acute episodes. Even when euthymic, many BD patients continue to demonstrate circadian disruptions, including diminished sleep efficiency and lower daytime activity levels (Plante, 2008). Moreover, unaffected offspring of BD patients demonstrate sleep and activity abnormalities (Ankers, 2009), and variation within several circadian-related genes (e.g. CLOCK) has been associated with risk for BD (Dallaspezia, 2009). These trait-like circadian disruptions are of particular clinical relevance as chances in sleep are highly predictive of impending affective instability (Plante, 2008) and BD patients with poor sleep quality report diminished quality of life (Gruber, 2009). Psychosocial treatments that incorporate the regulation of sleep and activity in BD have been successful in reducing recurrence, highlighting the important of stabilizing circadian rhythms in BD (Frank, 2005); yet treatment remains suboptimal and, to date, no pharmacological intervention using circadian measures as outcomes in BD has been published.

The exact nature of the circadian abnormality in BD is known; theories posit a potential uncoupling of the biological clock from external variables that entrain circadian rhythms (e.g. light) versus the desynchronization of the sleep-wake cycle such that it falls out of phase with other biological rhythms (Dallaspezia, 2009). Euthymic BD patients are commonly characterized by an eveningness chronotype, such that their time-to-sleep preference is phase-shifted to a later than average hour, one that is not typically aligned with the 24-hour light-dark cycle (Plante, 2008; Ahn, 2008). Potential consequences related to these persistent circadian abnormalities include significant reductions in daytime wakefulness and neurocognitive impairment.

While sleep deprivation induced by single-trial phase-shifts only impairs cognition until sleep in recovered, chronic deprivation such as those noted in BD individuals, have been implicated in significant learning and memory deficits in animal models (Craig, 2008). Moreover, humans who are unable to synchronize normal sleep-wakefulness schedules with their own internal biological clocks are impaired on tasks of processing speed, working memory, and learning (Wright, 2006). Indeed, a majority of BD patients demonstrate deficits in attention, memory, and executive function even when affectively stable (Goldberg \& Burdick, 2008). Although several features of the illness potentially contribute to the persistent cognitive impairment noted during euthymic periods, the circadian-based deficits in sleep quality and daytime wakefulness are likely to exacerbate cognitive problems in BD (Giglio, 2010), as has been shown in healthy controls, sleep disordered subjects and other clinical conditions (Benca, 2009). Preliminary data support this relationship in BD. The possible influence of chronic circadian disruption on cognition in BD is of critical importance because of a strong association between cognition during euthymic and functional disability (Sanchez-Moreno, 2009).

When considering agents that may simultaneously improve upon sleep quality and enhance cognition, the wake-promoting agents, modafinil, is an ideal candidate. It is FDA approved for improving wakefulness in adults with excessive daytime sleepiness due to primary sleep disorders (Provigil, 2007) and is characterized as a psychostimulant but has been differentiated from amphetamine by a lower liability for abuse and a more favorable risk profile. Modafinil has been shown to enhance cognition in healthy controls, sleep-disordered individuals, neurological patients, and patients with schizophrenia (Minzenberg, 2008). Preliminary data indicate that modafinil is safe and effective as an adjunctive in depressed BD patients, with no risk for mania-induction vs placebo (Frye, 2007); however there has not yet been a systematic trial in euthymic BD patients with sleep and cognitive dysfunction as outcome measures. Thus, adjunctive modafinil (200 mg/day) vs placebo will be administered to 48 euthymic patients with BD for 8 weeks with three specific aims:

1. To evaluate the safety of adjunctive modafinil in euthymic BD. Adverse events will be carefully measured and recorded in an effort to determine the base rates for common side effects in BD. Specifically, mood and psychosis ratings will be conducted weekly to address the potential for modafinil to exacerbate manic and/or psychotic symptoms.
2. To evaluate the effects of adjunctive modafinil in euthymic BD on measures of sleep quality and daytime wakefulness. Patients' subjective experience of sleep disruption and daytime wakefulness will be measured weekly using several standard questionnaires and daily diaries.
3. To evaluate the effects of adjunctive modafinil in euthymic BD on measures of neurocognition. Cognitive functioning will be assayed using the MATRICS Consensus Cognitive Battery supplemented by several domain-specific tasks at baseline, 4-weeks, and at the end of the 8-week study.