Controlled patterns of daytime light exposure improve circadian adjustment in simulated night work.

Circadian misalignment between the endogenous circadian signal and the imposed rest-activity cycle is one of the main sources of sleep and health troubles in night shift workers. Timed bright light exposure during night work can reduce circadian misalignment in night workers, but this approach is limited by difficulties in incorporating bright light treatment into most workplaces. Controlled light and dark exposure during the daytime also has a significant impact on circadian phase and could be easier to implement in real-life situations.

Effects of caffeine on daytime recovery sleep: A double challenge to the sleep-wake cycle in aging.

Background And Objective: Caffeine is the most widely used stimulant to counteract the effects of sleepiness, but it also produces important detrimental effects on subsequent sleep, especially when sleep is initiated at a time when the biological clock sends a strong waking signal such as during daytime. This study compares the effects of caffeine on daytime recovery sleep in young (20-30 y.) and middle-aged subjects (45-60 y.