0002 Detecting Sleep and Circadian Disruption in TBI Using Wearables

Abstract Introduction Traumatic brain injury (TBI) disrupts sleep and circadian rhythms, worsening cognitive and physiological impairments. Circadian dysfunction is difficult to measure and often mistaken for insomnia, leading to ineffective care. However, by capturing real-world diurnal patterns influenced by circadian biology, wearables offer potential to close this clinical gap. This study examines sleep-circadian interactions in sleep-deprived TBI and non-TBI participants. Methods Twenty-five participants (N=9 with TBI) were monitored at home for two weeks using the Oura ring. Diurnal rhythmic parameters, including acrophase and mesor, were derived from skin temperature via cosinor analysis. Midsleep time was calculated from sleep data. Participants completed the Insomnia Severity Index (ISI). After ~36 hours of sleep deprivation, participants underwent in-lab polysomnography (PSG) to assess sleep architecture. Linear regression models examined how TBI moderates relationships between circadian and sleep metrics (beta: interaction effect). Results Preliminary findings show TBI participants had significantly earlier diurnal rhythm timing, with acrophase at 1:55 AM vs. 3:02 AM in non-TBI participants (p 0.05). TBI status moderated the acrophase-midsleep relationship (beta=-0.5, p=0.033), suggesting disrupted circadian alignment. While PSG parameters and ISI showed no group differences, wearable-derived measures detected disruptions not captured in-lab. Early findings indicate weaker associations between circadian markers and restorative NREM sleep in TBI, suggesting impaired homeostasis. ISI scores revealed divergent insomnia–circadian coupling patterns between the groups. Conclusion Initial analysis suggests wearables can detect disruptions in circadian-influenced rhythms in TBI that may be missed in traditional clinical tests. Findings indicate earlier circadian timing and impaired sleep-circadian integration in TBI, particularly post-deprivation. Wearables offer a non-invasive way to identify subtle disruptions with clinical potential. Future work will clarify the relationship between changes in skin diurnal rhythms and the disruption of the gold-standard ‘pure’ circadian biology. Results underscore the need for targeted interventions addressing circadian and sleep dysfunction in TBI populations. Support (if any) Funding: CDMRPL-19-0-PR192622, W81XWH-22-2-0038. Disclaimer: The views, information or content, and conclusions presented do not represent the official position or policy of, nor should any official endorsement be inferred on the part of, the Uniformed Services University, the Department of War, the U.S. Government, or Walter Reed National Military Medical Center.