Evaluation of a portable light device for phase advancing the circadian rhythm in the home environment

This study evaluated the effectiveness of a head-mounted portable light device, Re-Timer, for phase advancing the circadian rhythm of healthy sleepers in the home environment. The Re-Timer was designed to address the limitations of traditional bright light boxes, making it more practical and efficient for administering light therapy. Eighteen healthy participants underwent a crossover design treatment protocol, consisting of seven consecutive mornings of using Re-Timer compared with the same procedure but not using Re-Timer. Circadian phase was measured using salivary dim light melatonin onset (DLMO) and subjective sleepiness was also assessed for other phase-change effects. After using the Re-Timer for seven mornings, a significant phase advance in DLMO of 41 min compared to a 10-min delay in the no-light control condition was observed. However, subjective sleepiness did not differ significantly between the two conditions. A few minor and transient side effects were experienced by participants, but no treatment was required. The Re-Timer is an effective and safe device for advancing the circadian rhythm of healthy sleepers at home. Future research on its clinical utility could make Re-Timer a practical and affordable way to self-administer bright light therapy for sleep disorders.