New Research: Bright Days Buffer Nighttime Light
A new study explores how bright daytime illumination can buffer the negative effects of nighttime light on sleep and circadian regulation. The research, which also reveals sex-based differences in this response, adds another layer of nuance to human-centric lighting strategies.
The research, conducted on mice at UCLA, found that bright daytime light at 300 lux largely prevented the negative circadian shifts and sleep disruptions caused by 10 lux of dim light at night. These effects were particularly pronounced in females, who otherwise showed significant phase shifts and rhythm attenuation under lower daytime light levels of 50 and 100 lux. This biological effect is driven by non-image-forming photoreceptors in the retina known as intrinsically photosensitive retinal ganglion cells (ipRGCs). These cells contain melanopsin, a photopigment that is critical for synchronizing the body's internal clock with the daily light-dark cycle, influencing hormone production, sleep, and mood. Standards like the WELL Building Standard v2 quantify this biological impact using the metric Equivalent Melanopic Lux (EML). Feature L03, Circadian Lighting Design, sets specific targets, such as providing at least 150 EML at eye level for four hours a day, to ensure lighting supports occupant health. Tunable white LED technology is
