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Updated: Jun 5, 2025

Human Circadian Phenotyping and Diurnal Performance Testing in the Real World
Published on: April 7, 2020
Effects of a daylight intervention in the morning on circadian rhythms and sleep in geriatric patients: a randomized
Anna Schubert1, Thea Laurentius2, Svenja Lange3
1Healthy Living Spaces Lab, Institute for Occupational, Social and Environmental Medicine, Medical Faculty, RWTH Aachen University, Pauwelsstraße 30, 52074, Aachen, Germany. anna.schubert@rwth-aachen.de.
Purpose:
During hospitalization, circadian rhythms and sleep are often disrupted, which has negative effects on health outcomes. Therefore, we aimed to investigate whether a daylight intervention in the morning could improve the circadian rhythms of cortisol and melatonin and enhance objective and subjective sleep quality in geriatric patients.
Methods:
The present study is a randomized, two-period crossover trial conducted in a geriatric ward in 15 non-demented geriatric trauma patients with a mean age of 83.1 ± 5.4 years. All patients underwent a daylight intervention period, during which they were exposed to a daylight lamp from 8:00 to 13:00 h, and a control period of 6 days each. Cortisol and melatonin levels were measured on day 5 of each period. Objective and subjective sleep quality were assessed using actigraphy and questionnaires, respectively. Within-participant differences between periods were investigated for all parameters.
Results:
A trend towards improvement in cortisol and melatonin rhythmicity was found. An increase in mean melatonin levels from 0.3 ± 0.1 to 0.9 ± 0.8 ng/L was observed during the intervention period (p = .063). There was also a trend towards increased sleep efficiency, whereas subjective sleep quality tended to decrease. None of the results were significant.
Conclusion:
A daylight intervention in the morning led to a positive trend in cortisol and melatonin rhythmicity, whereas no improvement in subjective sleep quality was found.
Trial Registration:
DRKS00028626 at German Clinical Trials Register, 13.06.2022.
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