Enhancing Precision Sleep Medicine in traumatic Brain Injury: Examining the feasibility of Home-Based Measurement of Circadian Timing

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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 sequelae such as depression, chronic pain, and fatigue. Current research suggests that TBI can impact numerous systems involved in sleep regulation, suggesting that insomnia may manifest from various etiologies and that a “one-size-fits-all” approach to treatment is likely inadequate. As such, it is necessary to differentiate Veterans who may benefit from standard evidence-based treatments, such as Cognitive Behavior Therapy for Insomnia, from those who 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 perturbations of key circadian rhythms involved in sleep regulation (e.g., melatonin production), as well as the manifestation 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 specialized sample (e.g., saliva) collection facilities and placing substantial burden on the patient. Recently, novel methods of DLMO measurement have been developed that may enhance the accessibility and practicality of circadian phase assessment, although, as of yet, they have not been used in Veterans with TBI. The proposed single-arm, longitudinal study seeks to evaluate the feasibility of two methods of measuring DLMO in the home environment of Veterans with TBI and insomnia: 1) direct measurement of self-collected salivary melatonin; and 2) indirect estimation of DLMO using activity and light- exposure data collected through actigraphy. Additionally, this study seeks to explore the relationships between circadian misalignment, sleep disturbance, and functional impairment in Veterans with TBI. The specific aims of this study are to: Aim 1) evaluate the feasibility of two methods of home DLMO measurement (i.e., self-collected salivary melatonin and actigraphy data) in Veterans with TBI and insomnia; and Aim 2) examine associations between circadian misalignment (i.e., the difference in timing between DLMO and attempted sleep onset), sleep disturbance, and functional impairment. Veterans with TBI and insomnia will be asked to wear a wrist-based actigraphy device for one week, which will collect data on light exposure and sleep-wake states. They will then be asked to self-collect seven hourly saliva samples under dim light conditions in their own home and mail them to a testing facility using a provided pre-paid shipping label. Saliva samples will be used to directly measure DLMO and actigraphy data will be used to indirectly estimate DLMO using established mathematical models of the human circadian pacemaker. Evaluating the feasibility of home DLMO measurement is a crucial first step for enhancing precision sleep medicine for Veterans with TBI and insomnia. Findings will inform the development and testing of tailored sleep interventions for use with this patient population.