Accepted for/Published in: JMIR mHealth and uHealth
Date Submitted: Apr 13, 2025
Date Accepted: Apr 13, 2026
Circadian entrainment and circadian disruption: the impact of sunlight and artificial light at night on sleep stages in a 7-day sensor-based observational study
ABSTRACT
Background:
Exposure to circadian entrainers, such as sunlight, positively impacts sleep architecture, while exposure before sleep time to circadian disruptors, like artificial light and smartphone use, can negatively affect sleep.
Objective:
This study aimed to investigate the effects of these factors on sleep duration and structure using sensor-based measurements over seven consecutive days.
Methods:
Twenty-one participants from the Jerusalem metropolitan area were monitored using the Dreem wearable electroencephalography for sleep staging, HOBO data loggers for light exposure, accelerometers for physical activity, and a dedicated mobile application to record smartphone usage. Multilevel mixed-effects models assessed the associations of daytime sunlight exposure, evening artificial light exposure, and smartphone use over the day with selected sleep outcomes the following night, adjusting for step counts and other individual covariates.
Results:
Each additional hour of daytime sunlight exposure was associated with an increase of 10.67 minutes in total sleep time (TST) the following night (95% CI: 0.64, 20.70) and with a 0.29 percentage point decrease in light sleep (N1) percentage (95% CI: -0.55, -0.03). No associations were found between evening artificial light exposure and sleep outcomes, while each minute of smartphone use before bed time was linked to an increased sleep onset latency of 0.20 minutes (95% CI: 0.00, 0.39).
Conclusions:
Promoting outdoor sunlight exposure during the day while limiting smartphone use in the evening may enhance sleep and circadian health. This study highlights the utility of sensor-based approaches in naturalistic settings for advancing sleep research.
Citation
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