COMBINING BLUE-GREEN LIGHT EXPOSURE AT NIGHT AND BLUE-BLOCKERS IN THE MORNING TO FACILATE ADAPTATION TO THE NIGHT SHIFT: FIRST FIELD STUDY

摘要

For a majority of work place, light intensityprovided during the night shift is insufficient to resynchronize the biological clock to a nighttime schedule. In addition, morning sunlight exposure tends to maintain the biological clock to a diurnal rhythm. This situation leads to difficulty in getting proper sleep during the day and be alert at night. It has been shown that increasing light intensity at night (>1000 lux at eye level) and wearing dark goggles (2percent of transmittance) in the morning can be used to facilitate adaptation to night work but these strategies are hardly applicable in real situations. Indeed, producing bright white light can be costly and can induce adverse effects following long expositions, such as eyes discomfort and headache whereas wearing dark goggles, can interfere considerably with vision, therefore raising safety concerns when driving. Recently, the biological clock has been shown to be more sensitive to the blue portion of the light spectrum (446 to 483 nm). By using specific stimulating blue-green light, it may be possible to lower the intensity of light necessary at night to give the biological clock a daytime signal. Additionally, wearing in the morning orange lens glasses that block all wavelengths below 540 nm (blue blockers) could impede the capacity of sunlight to give a resynchronizing daytime signal to the biological clock. Therefore, in the current study, we evaluated the impact of combining both strategies in a real workplace to see if indeed we could facilitate adaptation to the night shift schedule in workers affected to weekly rotations. In this study, the workers were exposed at night to a 200 lux blue-green light whereas in the morning, they had to wear blue blockers on their way home after the night shift. The main outcome was improvement on vigilance, subjective alertness, performance and adjustment of the biological clock (based on the melatonin rhythm).