Participants
MAY, JET LAG
Study participants were recruited by convenience sampling (via the electronic job platform of the University of Innsbruck) and snowball sampling and had to fulfill the following criteria for study inclusion: (1) age between 18 and 65 years, (2) no self-reported sleep problems, (3) habitual sleep duration of 7–9 h, (4) no extreme chronotype and social jet lag of less than 2 h (characterized by mid-sleep points on weekdays and days offBefore starting the study, a power analysis was performed using G*Power (version 3.1.9.6, University of Kiel, Germany). Assuming small to medium effect sizes of the light intervention (f = 0.15; seeData collection took place between March 15 and May 29, 2021, and subjects were financially compensated for participation in the study (total 130 €). The study protocol was approved by the Ethics Committee of the University of Innsbruck and strictly adhered to the principles of the 1968 Declaration of Helsinki. All subjects gave written informed consent before enrollment in the study.A total of 56 subjects (75% students) were included in the study. The sociodemographic data of the sample and the ratings of the seven subjective sleep quality dimensions for both study interventions are presented in Table Characterization of the study sample.Note: Numbers given in parentheses for subjective sleep quality indexes show either the range of the score, a binary answer category (yes), or sleep duration in hours (h).