Human Centric Lighting: The impact of light on sleep and attention of factory shift workers

Abstract

Abstract Introduction Increased blue-enriched morning light is often said to support circadian rhythm synchronization. Through a better sleep quality, one's cognitive and emotional functioning can also be enhanced. However, it is unclear which light characteristics (especially illuminance at eye level) are necessary to obtain a wellbeing effect in employees. This field study investigated different lighting conditions in a truck factory. Methods 71 shift workers participated in the study during their morning shift (6 am - 2 pm). Measurements of sleep (MotionWatch8), attention (D2 attention task, go no-go computer task) and visual comfort (questionnaire) were administered before and after changing the lighting conditions. A Human Centric Lighting-condition (HCL; vertical melanopic equivalent daylight illuminance (MEDI) = 250 lux, CCT=5000 K; N = 33) was compared with a control LED-condition (MEDI = 44 lux, CCT=4000K; N = 38). Results Results show that workers in the HCL-condition showed a larger improvement in sleep efficiency (p=.057) and concentration (p=.01) than the control LED-group. No differences were found in visual comfort between groups. Discussion Preliminary results are promising and show that 250 MEDI might be a sufficient cut-off to stimulate workers' sleep and cognition. The high illuminance level was not detrimental in the HCL condition for the perceived visual comfort. Key messages Blue-enriched morning light supports sleep and concentration in shift workers. High illuminance levels are not detrimental for the perceived visual comfort.