Influence of artificial dusk on sleep

The aim of the study was to elucidate an influence of artificial dusk on sleep of healthy sleepers. Twenty-six participants with a normal 5–6-day weekly active schedule, sleeping single in bedroom and naive to the primary aim of the study, completed two consecutive arms, each consisting of 7 days baseline, 13 days intervention, and 8 days follow-up. The intervention was dawn and dusk simulation (dusk) compared to dawn and a rectangular light–dark switch prior to sleep time (lights off). The 30-min dusk signal was preceded by 10 min of constant light to be similar in the overall light dose to the 17-min lights off signal. Throughout the study, subjects filled out a sleep diary immediately before and after sleep and wore actiwatches. Saliva for melatonin ELISA and circadian phase estimation was sampled prior to bedtime at home on days 7 or 8, 13 or 14 and 20 of each arm. Circadian phase remained unchanged throughout the study. Of the thirteen variables analysed, only one showed a difference: the number of minutes with movements during the first 40 min of the sleep episode was lower after dusk presentation compared to both lights off presentation and pre- and post-dusk days (P