Bright days, dark nights: translating science on the non-visual effects of light into public health guidance

Maya Piper; Kai Broszio; Jan Denneman; Marijke Gordijn; Elise McGlashan; Renske Lok; Raymond P Najjar; Luke Price; David Sliney; Oliver Stefani; Juliette van Duijnhoven; Laura Kervezee; Manuel Spitschan

doi:10.3389/phrs.2026.1609683

Bright days, dark nights: translating science on the non-visual effects of light into public health guidance

Public Health Rev. 2026 Jul 7:47:1609683. doi: 10.3389/phrs.2026.1609683. eCollection 2026.

Authors

Maya Piper¹, Kai Broszio², Jan Denneman³, Marijke Gordijn^{4

5}, Elise McGlashan⁶, Renske Lok⁷, Raymond P Najjar^{8

9}, Luke Price¹⁰, David Sliney¹¹, Oliver Stefani¹², Juliette van Duijnhoven¹³, Laura Kervezee¹⁴, Manuel Spitschan^{15

16

17

18}

Affiliations

¹ Light for Public Health Initiative, Munich, Germany.
² Federal Institute for Occupational Safety and Health (BAuA), Dortmund, Germany.
³ Good Light Group, Eindhoven, Netherlands.
⁴ Chrono@Work, Groningen, Netherlands.
⁵ Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, Netherlands.
⁶ Melbourne School of Psychological Sciences, The University of Melbourne, Parkville, VIC, Australia.
⁷ Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO, United States.
⁸ Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
⁹ Singapore Eye Research Institute, Singapore, Singapore.
¹⁰ UK Health Security Agency, London, United Kingdom.
¹¹ Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MA, United States.
¹² Lucerne University of Applied Sciences and Arts, Lucerne, Switzerland.
¹³ Department of the Built Environment, Building Lighting group, Eindhoven University of Technology, Eindhoven, Netherlands.
¹⁴ Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, Netherlands.
¹⁵ Max Planck Institute for Biological Cybernetics, Translational Sensory & Circadian Neuroscience, Tübingen, Germany.
¹⁶ TUM School of Medicine and Health, Technical University of Munich, Munich, Germany.
¹⁷ TUM Institute for Advanced Study (TUM-IAS), Technical University of Munich, Garching, Germany.
¹⁸ TUMCREATE Ltd., Singapore, Singapore.

Abstract

Background: Light is a daily environmental exposure that can influence circadian timing, sleep, alertness, mood, and cognition, yet public health guidance still focuses mainly on optical-radiation hazards rather than healthy patterns of visible light and darkness.

Analysis: This policy brief translates recent evidence and expert consensus on the non-visual effects of ocular light exposure into public health guidance. The evidence supports a practical 24-h pattern: brighter light during the morning and daytime, lower light in the evening, and darkness or near-darkness during sleep. This principle should be communicated as general guidance rather than a universal dose, because responses vary with timing, intensity, spectrum, duration, prior light exposure, age, work schedules, health status, and geography.

Policy options: Public health organizations can communicate plain-language guidance, integrate light into workplaces, schools, healthcare, elder care, housing, and public buildings, align daylight messages with sun-safety advice, and support research, measurement, and melanopic labeling.

Conclusion: Clear, proportionate guidance on light and darkness can help people and institutions structure daily environments to support circadian alignment, sleep, alertness, mental health, and wellbeing.

Keywords: chronobiology; circadian rhythm; consensus statements; daylight; health guidelines.