Human phase response curve to intermittent blue light using a commercially available device.
ABSTRACT Key points Misalignment between the internal circadian clock driving daily rhythms in physiology and behaviour, such as sleepiness, performance and metabolism, and the sleep-wake schedule, as occurs in jet lag and night shift work, can have profound, harmful consequences for health, performance and safety. Light applied at specific times of day can be used to shift the timing of the clock and reduce this circadian misalignment. We show for the first time that a small, commercially available, portable blue light device is capable of shifting the clock when it is administered daily over a 2 h window (90 min blue light as 30 min pulses with 15 min breaks). The direction and amount that the clock is shifted depends on the time of day that the light is administered. The results of this work provide a practical, effective light treatment that can be used in the real world.