Abstract Number: Esoc2026a396 Diurnal Rhythm of Activity and Melatonin in Stroke Patients Admitted for Rehabilitation and the Influence of Naturalistic Hospital Lighting

Abstract Background and aims Circadian disruption is common after stroke, but its impact on diurnal activity during rehabilitation of stroke patients is unclear. This study aimed to examine changes in diurnal activity and melatonin rhythms during stroke rehabilitation, their interrelationship, and the influence of in-hospital lighting. Methods Between May 1, 2014, and June 1, 2015, 29 patients were randomized to rehabilitation with naturalistic lighting (n=16) or standard indoor lighting (n=13). Diurnal activity was measured by actigraphy on the non-paretic arm for seven consecutive days at admission and discharge. Plasma melatonin was sampled at seven time points over a 24-hour period at admission and discharge. Results From admission to discharge, relative nighttime activity decreased compared with daytime activity (mean change −5.12, 95% CI −10.2 to −0.002; p=0.0499), indicating partial restoration of diurnal activity rhythms. At admission, lower night-to-day activity was associated with higher night-to-day melatonin (β −1.78, 95% CI −3.09 to -0.46; p=0.0099). This association was not observed at discharge due to a decrease in nighttime melatonin during hospitalization (median change −3.5, IQR −9.1 to 1.17; p=0.0111). Exposure to naturalistic lighting was not associated with significant changes in activity or melatonin rhythmicity compared with standard indoor lighting. Conclusions Diurnal activity rhythms showed partial restoration during admission, whereas diurnal melatonin rhythms appeared increasingly disrupted. The relationship between activity and melatonin observed at admission was no longer present at discharge, suggesting a disruption of the circadian system during hospitalization. Naturalistic lighting was not associated with measurable changes in diurnal activity or melatonin, possibly due to the small sample size. Conflict of interest Frederik Winsløw: nothing to disclose, Poul Jørgen Jennum: nothing to disclose, Helle Klingenberg Iversen: nothing to disclose, Anders Sode West: nothing to disclose.