0641 Predicting Circadian Phase Shift: Circadian Monitoring and Regulation System

• Published in: Sleep (New York, N.Y.) Vol. 41; no. suppl_1; p. A238
• Main Authors: Rea, M S, Jones, G, Hovareshti, P, Tolani, D, Bierman, A, Figueiro, M G
• Format: Journal Article
• Language: English
• Published: US Oxford University Press 27.04.2018
• Subjects: Circadian rhythm; Jet lag; Light; Sensors
• ISSN: 0161-8105; 1550-9109
• DOI: 10.1093/sleep/zsy061.640

Abstract Introduction The Circadian Monitoring and Regulation (CMR) system is comprised of a light sensor worn as a button on the collar or shirt and an activity sensor worn on the wrist. A modified Kronauer model of human circadian entrainment (circadian stimulus, CS-oscillator model) was incorporated into an app to deliver a light prescription to advance or delay circadian phase. The CS-oscillator model uses personal light exposures to predict circadian phase. The phone app is connected to the light and activity sensor via Bluetooth. The goal of the present study was to determine whether the CMR system delivering a light prescription designed to advance the circadian phase of participants by 4 hours would lead to similar phase advance in the dim light melatonin onset (DLMO). Methods Sixteen subjects were recruited for the study. Saliva samples were collected for 15 subjects (10 female, 5 male, age 25.4 +/- 6.6 years), and data from the system were obtained from 11 subjects. Light and activity data were collected for 14 days immediately before the 14 intervention days (baseline) and during the intervention period. Saliva samples were collected for DLMO measurement at the conclusions of the baseline period and the intervention period. Results Based upon DLMOs measured right after baseline and right after intervention, all subjects advanced their circadian phase, but by less than the intended 4 hours. The smaller then intended phase changes are likely because the subjects did not alter their sleep and wake times. Conclusion The CMR system using the CS-Oscillator model can predict changes in circadian phase based upon actual light exposures. However, it was not possible to advance subjects by 4 hours because they did not change their rest activity patterns from baseline to intervention. We infer that social constraints limit the ability of light-induced phase changes to alter behavior. Future studies should investigate whether controlling both light-dark patterns and sleep schedules can lead to a greater phase change than controlling light-dark patterns only. Support (If Any) Sponsor: Army Research Office.