EVENING DAYLIGHT MAY CAUSE ADOLESCENTS TO SLEEP LESS IN SPRING THAN IN WINTER

Abstract

Sleep restriction commonly experienced by adolescents can stem from a slower increase in sleep pressure by the homeostatic processes and from phase delays of the circadian system. With regard to the latter potential cause, the authors hypothesized that because there is more natural evening light during the spring than winter, a sample of adolescent students would be more phase delayed in spring than in winter, would have later sleep onset times, and because of fixed school schedules would have shorter sleep durations. Sixteen eighth-grade subjects were recruited for the study. The authors collected sleep logs and saliva samples to determine their dim light melatonin onset (DLMO), a well-established circadian marker. Actual circadian light exposures experienced by a subset of 12 subjects over the course of 7 days in winter and in spring using a personal, head-worn, circadian light measurement device are also reported here. Results showed that this sample of adolescents was exposed to significantly more circadian light in spring than in winter, especially during the evening hours when light exposure would likely delay circadian phase. Consistent with the light data, DLMO and sleep onset times were significantly more delayed, and sleep durations were significantly shorter in spring than in winter. The present ecological study of light, circadian phase, and self-reported sleep suggests that greater access to evening daylight in the spring may lead to sleep restriction in adolescents while attending school. Therefore, lighting schemes that reduce evening light in the spring may encourage longer sleep times in adolescents. (Author correspondence: [email protected])

Keywords:

• Adolescents
• Circadian rhythms
• DLMO
• Light measurement
• Sleep restriction

ACKNOWLEDGMENTS

The authors would like to acknowledge the U.S. Green Building Council (USGBC) for sponsoring this research. Support for the work presented here was also given by the Trans-NIH Genes, Environment and Health Initiative Grant U01 DA023822, and the Office of Naval Research (ONR). The authors would also like to thank Dr. Mary Carskadon and Dr. Stephanie Crowley of Brown University and Bradley Hospital for helping with the DLMO calculations. Dr. Christopher Steele (ONR) is also acknowledged for lending the PDAs for the study, although these data are not reported here. Andrew Bierman, Jennifer Brons, Brian Dolan, Dennis Guyon, Ranjith Kartha, Terry Klein, Karen Kubarek, Nick Meyer, Barbara Plitnick, Dan Wang, and Brittany Wood of the Lighting Research Center and Kathleen Ackerbauer of Russell Sage College are acknowledged for their contributions to this project. We would also like to thank the staff, teachers, and principal of Algonquin Middle School for making this project possible. We would also like to thank the students and parents who participated in this research project.

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