Intermittent exposure to bright light in field conditions.

The Interactive Neurobehavioral Model integrates Kronauer's and Jewett's latest mathematical model of the resetting effect of light on the human circadian pacemaker. This model is based on several lines of experimental evidence and considers the endogenous circadian pacemaker as a complex oscillatory system that responds dynamically to the resetting effect of light. This model can help us understand the results of an experiment using intermittent bright light exposure in the workplace environment. Intermittent exposure to bright light was effectively used as part of an intervention to promote circadian re-entrainment of a group of nurses to their permanent night work schedule. Regular exposure to lower light levels and darkness also provided a significant phase delay of endogenous circadian rhythms, although the adaptation was incomplete in this group of workers. These last results are consistent with the intensity-dependent component of the model. The development of better tools to measure retinal exposure to light throughout the 24-h day is required to adequately test modeling predictions under field conditions.