1144 PRESENCE OF MELATONIN RHYTHM IN ACUTE MODERATE-SEVERE TRAUMATIC BRAIN INJURY DESPITE SEVERE SLEEP-WAKE DISTURBANCES

Abstract

Introduction: Sleep-wake disturbances (SWD) are present in the acute phase of moderate-severe traumatic brain injury (TBI), and could be related to circadian disturbances caused by the brain injury. The goal of this study was to 1) compare the rest-activity and melatonin rhythms of moderate-severe TBI patients to that of patients with severe orthopedic and/or spinal cord injuries (OSCI); and 2) evaluate the association between melatonin and the sleep-wake cycle in TBI patients. Method(s): Seventeen moderate-severe TBI patients (Glasgow Coma Scale score: 6.8 +/- 3.3; 30.3 +/- 13.3yo; 14 men) and sixteen OSCI patients (30.9 +/- 13.2yo; 13 men) were recruited in intensive care. Urine was collected from their urinary catheter every hour for 25 hours starting 18.7 +/- 12.3 days post-injury, and concentration of 6-sulfatoxymelatonin was calculated to obtain area under the curve (AUC)(ng). A cosinor analysis was also carried out to obtain amplitude (ng/ml) and acrophase (h). Patients wore wrist actigraphs for 9.4 +/- 4.2 days, starting 19.3 +/- 12.6 days post-injury. Average nighttime (22:00-6:59) sleep duration and fragmentation index were calculated. The daytime activity ratio was used to quantify rest-activity cycle consolidation. We compared groups on actigraphy and melatonin variables using Student's t-tests. Among TBI patients, we investigated associations between melatonin and actigraphy variables using Pearson's correlations. Statistical significance was set at p<0.01. Result(s): TBI patients had shorter nighttime sleep duration (TBI: 345.8 +/- 101.2mins; OSCI: 449.0 +/- 54.4mins, t(30)=-3.52, p<0.01), higher fragmentation index (TBI: 80.5 +/- 34.0; OSCI: 52.6 +/- 23.3, t(30)=2.68, p=0.012), and poorer rest-activity cycle consolidation (TBI: 75.8 +/- 9.3%; OSCI: 86.1 +/- 4.8%, t(30)=-3.87, p<0.001). A melatonin rhythm was present in TBI patients, and no group differences were found for AUC (TBI: 249.5 +/- 165.6ng; OSCI: 162.3 +/- 88.9ng), amplitude (TBI: 12.0 +/- 7.5ng/ml; OSCI: 7.7 +/- 4.8ng/ml), and acrophase (TBI: 5:08 +/- 2:14; OSCI: 5:59 +/- 3:16)(p-values>0.05). No associations were found between melatonin and actigraphy variables in TBI patients (p-values>0.01). Conclusion(s): This study shows that despite having more severe SWD, moderate-severe TBI patients have a melatonin rhythm similar to other trauma patients without a brain injury. Moreover, SWD do not seem to be associated to melatonin rhythm. This suggests that neural mechanisms other than the circadian system may be responsible for post-TBI SWD.