MODIFICATIONS TO WEEKEND RECOVERY SLEEP DELAY CIRCADIAN PHASE IN OLDER ADOLESCENTS

Abstract

Adolescents often report shorter time in bed and earlier wake-up times on school days compared to weekend days. Extending sleep on weekend nights may reflect a “recovery” process as youngsters try to compensate for an accumulated school-week sleep debt. The authors examined whether the circadian timing system of adolescents shifted after keeping a common late weekend “recovery” sleep schedule; it was hypothesized that a circadian phase delay shift would follow this later and longer weekend sleep. The second aim of this study was to test whether modifying sleep timing or light exposure on weekends while still providing recovery sleep can stabilize the circadian system. Two experiments addressed these aims. Experiment 1 was a 4-wk, within-subjects counterbalanced design comparing two weekend sleep schedule conditions, “TYPICAL” and “NAP.” Compared to weeknights, participants retired 1.5 h later and woke 3 h later on TYPICAL weekends but 1 h later on NAP weekends, which also included a 2-h afternoon nap. Experiment 2 was a 2-wk, between-subjects design with two groups (“TYPICAL” or “LIGHT”) that differed by weekend morning light exposure. TYPICAL and LIGHT groups followed the TYPICAL weekend schedule of Experiment 1, and the LIGHT group received 1 h of light (454–484 nm) upon weekend wake-up. Weekend time in bed was 1.5 h longer/night than weeknights in both experimental protocols. Participants slept at home during the study. Dim light melatonin onset (DLMO) phase was assessed in the laboratory before (Friday) and after (Sunday) each weekend. Participants were ages 15 to 17 yrs. Twelve participants (4 boys) were included in Experiment 1, and 33 (10 boys) were included in Experiment 2. DLMO phase delayed over TYPICAL weekends in Experiment 1 by (mean ± SD) 45 ± 31 min and Experiment 2 by 46 ± 34 min. DLMO phase also delayed over NAP weekends (41 ± 34 min) and did not differ from the TYPICAL condition of Experiment 1. DLMO phase delayed over LIGHT weekends (38 ± 28 min) and did not differ from the TYPICAL group of Experiment 2. In summary, adolescents phase delay after keeping a commonly observed weekend sleep schedule. Waking earlier or exposure to short-wavelength light on weekend mornings, however, did not stabilize circadian timing in this sample of youngsters. These data inform chronotherapy interventions and underscore the need to test circadian phase-shifting responses to light in this age group. (Author correspondence: [email protected])

Keywords:

• Adolescent
• Circadian rhythms
• DLMO phase
• Light
• Nap
• Weekend sleep pattern

ACKNOWLEDGMENTS

This work was supported by a predoctoral Ruth L. Kirschstein National Research Service Award (NRSA) from the National Institutes of Mental Health (NIMH) (1 F31 MH078662-01) awarded to S. Crowley and a grant from Apollo Health, Inc., awarded to S. Crowley. We thank Christine Acebo, PhD, Ronald Seifer, PhD, Russell Church, PhD, and David Berson, PhD, for their insightful comments on this project, Isaac Gross and Jacqueline Muñoz for assisting with data collection, and Denise Maceroni for analyzing saliva samples for melatonin. We would also like to acknowledge the participants and their families for their dedication and cooperation while participating 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.