# Effects of a daylight intervention in the morning on circadian rhythms and sleep in geriatric patients: a randomized crossover trial

## TL;DR

This study tested if morning daylight exposure improves circadian rhythms and sleep in elderly patients, finding some positive trends but no significant sleep quality improvement.

## Contribution

The study introduces a randomized crossover trial examining the effects of morning daylight on circadian rhythms in geriatric patients.

## Key findings

- A trend towards improved cortisol and melatonin rhythmicity was observed during the daylight intervention.
- Subjective sleep quality did not improve, and some objective sleep measures showed mixed results.
- No statistically significant differences were found between the intervention and control periods.

## Abstract

To explore whether a daylight intervention could improve the circadian rhythms of cortisol and melatonin in geriatric patients, alongside their sleep quality.

The results indicated a tendency towards an enhancement of the endocrinological parameters' circadian rhythms. However, there was no improvement in subjective sleep quality following the intervention.

A daylight intervention could be of value in enhancing the circadian rhythms of geriatric patients.

The online version contains supplementary material available at 10.1007/s41999-024-01100-z.

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.

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.

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.

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.

DRKS00028626 at German Clinical Trials Register, 13.06.2022.

The online version contains supplementary material available at 10.1007/s41999-024-01100-z.