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Abstract Introduction Night shift workers experience symptoms of excessive sleepiness and insomnia due to misalignment between their circadian clock and work schedule. Circadian misalignment can be corrected using exposure to bright light delivered in accordance with a phase response curve. Our prior data indicate that a light schedule personalized to an individual’s melatonin rhythms produces greater reductions in circadian misalignment compared to a one-schedule-fits-all approach. This randomized controlled trial extends prior findings by examining the effect of personalized light therapy on symptoms of shift work disorder. Methods Individuals with shift work disorder (ICSD-3 diagnostic criteria) were randomized into two conditions: personalized light therapy (n = 14), or a non-personalized light therapy control (n = 7). Personalized light schedules were based on estimates of dim light melatonin onset (DLMO) derived from mathematical modeling of data collected via an Apple Watch. Light schedules were delivered through a mobile app (Arcashift) that updated in accordance with real-time estimates of DLMO. Estimates were confirmed with in-lab DLMO. Participants were provided light blocking glasses and a light box as source of bright light at night. Sleepiness (Karolinska Sleepiness Scale) and insomnia (Insomnia Severity Index) were assessed before and after treatment, and analyses evaluated change scores from pre- to post-treatment. Results Those in the personalized light therapy group demonstrated decreased insomnia symptoms during daytime sleep (mean = -4.64, SD = 8.03) compared to those in the non-personalized control (mean = 3.57, SD = 5.38), p 0.05. The personalized light therapy group also achieved a decrease in peak sleepiness (mean = -0.21, SD = 0.68) compared to the control (mean = 0.77, SD = 0.76), p .001. Conclusion Preliminary results suggest that personalizing light therapy according to the individual’s specific circadian phase may be more effective in improving symptoms of insomnia and sleepiness by delivering treatment. Future research should examine other occupational and health outcomes associated with a personalized approach to light therapy. Support (if any) Support for this study was provided from the National Institute of Health R41HL163783 and the American Academy of Sleep Medicine Foundation (245-SR-21) awarded to Drs. Philip Cheng and Olivia Walch.
Paniccia et al. (Sat,) studied this question.