Literature review on circadian lighting (research report) (2017) (pdf)

This BRE Client Report, B137170-01 (Dated Jan 2017) is made by BRE from a project jointly funded by CIBSE and the BRE Trust.
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Exposure to light, particularly blue light, has been shown to maintain, or potentially alter the body’s circadian clock. The lighting industry has recently started to market circadian lighting, using tuneable (most commonly LED) white light sources that can alter their light colour and intensity. The aim is to help maintain correct timing of the circadian clock of the occupants in a space; to improve their alertness during the day or during working hours, then change to lower brightness, warmer coloured lighting when it is time to relax. However little or no research has been done on the best way to control this tuneable lighting under real-world conditions.

With this in mind, a project jointly funded by CIBSE and the BRE Trust ‘Circadian lighting effects on health and wellbeing’ has been initiated. The project will investigate when is the best time to have the high intensity, cool coloured lighting, and for how long, and when to turn it down and make it warmer. The project aims to find optimal control strategies for circadian lighting to maximise health and wellbeing benefits.

This report, the first output of the project, provides a review of the existing literature on circadian lighting and how this affects human health and wellbeing. It incorporates findings from a workshop on circadian lighting, held at BRE on 29 September 2016 as part of the project. The workshop was attended by leading professionals from academia, manufacturers, lighting designers and public health institutions.

Much recent research has looked at the effects on wellbeing and health of disruption to the circadian clock. Levels of artificial lighting may be too low during the day, or contain insufficient blue light to maintain circadian rhythms. Conversely, inappropriate exposure to light, particularly light at night in the blue wavelength range, is likely to disrupt the circadian system and lead to a range of disorders and health problems.

Daylight gives high levels of blue enriched light and changes in colour and intensity over the day, which makes it ideal for modulating circadian rhythms. Various studies have shown positive effects of daylight on health, stress and mood. In principle, exposure to bright artificial light at the correct times of day could have similar effects.

Contents:

Introduction
Literature review on circadian lighting
Human circadian system
Impact of light spectrum on circadian rhythms and performance
Circadian disruption and impacts on human health
Exposure to daylight in buildings
Effects of bright artificial lighting
Existing research on circadian/dynamic/variable lighting
Measures of circadian lighting
Circadian lighting workshop
Conclusion
References
Appendix A Circadian lighting workshop: Agenda

Acknowledgements
Author: Cosmin Ticleanu (Principal Consultant (Lighting, (BRE)
Authorised by: Paul Littlefair (Lighting, BRE)