This project examines 1) the effects of appropriately timed bright light on adaptation (in terms of sleep and sleepiness) to three consecutive night shifts; and 2) the effects of such bright light on re-adaptation (in terms of sleep and sleepiness) to a day-oriented schedule after the night shift period.

Shift workers frequently experience sleepiness during night shifts, which may have consequences for performance. Sleep duration is often shortened after a night shift. Properly timed bright light treatment is efficient in delaying the circadian rhythm and can enhance alertness, increase performance and prolong sleep after night shifts. There is a lack of studies on light treatment to rotating shift workers. This study is a randomized controlled crossover trial evaluating the effect of bright light treatment on sleep and sleepiness in rotating shift workers with three consecutive night shifts. The aim is to evaluate whether bright light treatment improves adaptation to three consecutive night shifts (reduces sleepiness during night shifts and improves sleep after night shifts), as well as whether such treatment affects re-adaptation to a day-oriented schedule after the night shift period.

Inclusion Criteria:

• A rotating shift work schedule involving three days without night shifts, followed by three consecutive night shifts, followed by three days without night shifts
• Problems with sleepiness during night shifts

Exclusion Criteria:

• Pregnancy