Exposure to Bright Light and Darkness to Treat Physiologic Maladaptation to Night Work

Abstract

Abstract Working at night results in a misalignment between the sleep–wake cycle and the output of the hypothalamic pacemaker that regulates the circadian rhythms of certain physiologic and behavioral variables. We evaluated whether such physiologic maladaptation to nighttime work could be prevented effectively by a treatment regimen of exposure to bright light during the night and darkness during the day. We assessed the functioning of the circadian pacemaker in five control and five treatment studies in order to assess the extent of adaptation in eight normal young men to a week of night work. In the control studies, on the sixth consecutive night of sedentary work in ordinary light (approximately 150 lux), the mean (±SEM) nadir of the endogenous temperature cycle continued to occur during the night (at 03:31 ±0:56 hours), indicating a lack of circadian adaptation to the nighttime work schedule. In contrast, the subjects in the treatment studies were exposed to bright light (7000 to 12,000 lux) at night...