The timing of daytime sleep, and thus the timing of daytime light exposure, affects the size and direction of the phase shift induced by a week of night shifts

The aim of the study was to examine how the timing of daytime sleep in the dark, and thus the timing of daytime light exposure, affects circadian adaptation to a week of simulated night shifts. It was hypothesised that night work would delay the circadian system - and the size of the delay would increase as the duration of exposure to light in the morning and early-afternoon decreased.