The impact of Emel range of dynamic lighting on alertness, fatigue and sleeping quality

Our earlier works found dynamic lighting to have some positive effect on alertness and circadian response comparing with static light. This study further investigates different CCT ranges and melanopicilluminance (Emel) or circadian stimulus (CS) of dynamic lightings. Sixteen subjects participated the experiment including 4 lightings, one each day from 20:30 to 23:00, and 4 days apart between each lighting. Four different lightings include two CCT ranges (from 6000K to 12000K and from 3000K to 9000K), each having a low and a high Emel level. Six testing methods were included task performance (the D2 test, go/no go), Critical Flicker Frequency (CFF), ocular fatigue questionnaire, sleepiness (Karolinska sleepiness scale), biochemical responses (melatonin and cortisol). The results showed that subjects were statistically significant more alert under high Emel lightings from the results of task performance, CFF, and both biochemical responses. As for the KSS and ocular-fatigue results, subjects felt sleepier and less fatigue under both low Emel and low CCT range lightings. The strong duration effect was revealed from the results of KSS, ocular fatigue and biochemical responses.