Outdoor Light at Night (LAN) Is Correlated With Eveningness in Adolescents

Abstract

External zeitgebers synchronize the human circadian rhythm of sleep and wakefulness. Humans adapt their chronotype to the day-night cycle, the strongest external zeitgeber. The human circadian rhythm shifts to evening-type orientation when daylight is prolonged into the evening and night hours by artificial light sources. Data from a survey of 1507 German adolescents covering questions about chronotype and electronic screen media use combined with nocturnal satellite image data suggest a relationship between chronotype and artificial nocturnal light. Adolescents living in brightly illuminated urban districts had a stronger evening-type orientation than adolescents living in darker and more rural municipalities. This result persisted when controlling for time use of electronic screen media, intake of stimulants, type of school, age, puberty status, time of sunrise, sex, and population density. Time spent on electronic screen media use—a source of indoor light at night—is also correlated with eveningness, as well as intake of stimulants, age, and puberty status, and, to a lesser degree, type of school and time of sunrise. Adequate urban development design and parents limiting adolescents' electronic screen media use in the evening could help to adjust adolescents' zeitgeber to early school schedules when they provide appropriate lighting conditions for daytime and for nighttime. (Author correspondence: [email protected])

Keywords:

• Adolescents
• Chronotype
• CSM
• Electronic screen media
• Intake of stimulants
• Light at night (LAN)
• Light pollution
• Midpoint of sleep
• Remote sensing

ACKNOWLEDGMENTS

This study was supported by grant no. 70131211, University of Education, Heidelberg. We would like to thank the editor and reviewers for their helpful annotations. We are grateful to principals, teachers, and parents who supported the study and especially all pupils for participating; Farina Pötsch for visiting participating schools; and Caroline Buhmann, Farina Pötsch, and Lena Saliger for feeding the computer.

Declaration of Interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.