The Feasibility of Home-Based Measurement of Circadian Timing for Veterans With TBI and Insomnia

Veterans with traumatic brain injury (TBI) frequently experience insomnia, which is linked with delayed TBI recovery, more severe functional impairment, and exacerbation of disabling TBI after-effects such as depression, chronic pain, and fatigue. Current research suggests that TBI can impact numerous systems involved in sleep, suggesting that insomnia can have various causes and that a "one-size-fits-all" approach to treatment is likely inadequate. As such, it is necessary to determine which Veterans may benefit from standard evidence-based treatments, such as Cognitive Behavior Therapy for Insomnia, and which may require enhanced treatments targeting specific underlying mechanisms. An emerging body of evidence has established a link between circadian rhythm disruption and post-TBI insomnia. A mismatch between circadian and desired sleep timing (i.e., "circadian misalignment") is common following TBI, as evidenced by disruptions of key circadian rhythms involved in sleep regulation (e.g., melatonin production), as well as the onset of circadian rhythm sleep-wake disorders. Importantly, circadian-driven sleep disturbances require specialized treatments that target circadian rhythms (i.e., "chronotherapies"), such as timed sleep windows or enhanced light exposure, as standard treatment approaches can fail to address or even exacerbate the underlying circadian misalignment. Thus, circadian misalignment represents a novel and modifiable treatment target and has the potential to improve functional outcomes in Veterans with TBI and insomnia. Detection of circadian misalignment and optimal use of chronotherapies require the ability to measure circadian phase (i.e., timing of the central circadian clock). However, current sleep medicine in TBI is hampered by a lack of pragmatic options for measuring circadian phase. This is because laboratory dim light melatonin onset (DLMO), the gold standard measure of circadian phase, is time and cost prohibitive, requiring specialize