The 2nd International Workshop on Circadian and Neurophysiological Photometry in 2019 brought together 18 experts in lighting, neurophysiological photometry, sleep and circadian research. These scientists agreed on recommendations for daytime light and evening light in indoor environments in a recent preprint publication. The most remarkable result is that they reached consensus on much higher values of light indoors during daytime and much more darkness during evening and nights than currently applied. The current situation of indoor lighting practices is not helpful for people’s health and well-being.
The recommendations mean in practice that indoor light levels during daytime needs to be increased with at least a factor 3-4 in order to have a healthy influence on the circadian rhythm of the users, sleep quality and daytime fitness.
From the publication:
Daytime light recommendations for indoor environments
Throughout the daytime, the recommended minimum melanopic EDI is 250 lx at the eye measured in the vertical plane at ~ 1.2 m height (i.e., vertical illuminance at eye level when seated).
If available, daylight should be used in the first instance to meet these levels. If additional electrical lighting is required, the polychromatic white light should ideally have a spectrum that, like natural daylight, is enriched in shorter wavelengths close to the peak of the melanopic action spectrum – 480 nm.
Evening light recommendations for residential and other indoor environments
During the evening, starting at least three hours before bedtime, the recommended maximum melanopic EDI is 10 lux measured at the eye in the vertical plane ~ 1.2 m height.
To help achieve this, where possible, the white light should have a spectrum depleted in short wavelengths close to the peak of the melanopic action spectrum – 480 nm.
In addition, the scientists stated:
Exposure to a stable and regular daily light-dark cycle is also likely to reinforce good alignment of circadian rhythms, which may further benefit sleep, cognition and health. These recommendations should therefore be applied at the same time each day, so far as possible.
These recommendations are not intended to supersede existing guidelines relating to visual function and safety. The non-visual ocular light responses covered here should be an additional level of consideration provided that relevant visual standards can still be met.
These recommendations are intended to apply to adults with regular daytime schedules. Special considerations may apply to specific populations (e.g. children, the elderly, shift workers) as discussed in the publication.