[P18] A red visor-cap prevents melatonin suppression by light during simulated night work

• Published in: Journal of PHYSIOLOGICAL ANTHROPOLOGY Vol. 29; no. 5; p. 177
• Main Authors: Fukuda T, Kinjo Y, Kozaki T, Miura N, Takahashi M, Higuchi S
• Format: Journal Article
• Language: Japanese
• Published: Japan Society of Physiological Anthropology 2010
• ISSN: 1880-6791

Bright light at night improves the alertness of night workers. Melatonin suppression by light at night is, however, reported to be possible risk factor of cancer. A red visor-cap is expected to prevent melatonin suppression by blocking off short wavelength light having a strong impact on melatonin suppression, with no change of color and brightness in the visual field. The purpose of this study was to investigate the effects of a red visor-cap on melatonin suppression and alertness during simulated night work. Eleven healthy male students (mean age: 21.2±0.9 yr) volunteered to participate in this study. On the first day, subjects spent time in dim light (<15 lux) from 20:00 to 03:00 to measure the baseline data of nocturnal change in salivary melatonin concentration. On the second day, subjects were exposed to light for 4 h from 23:00 to 3:00 with no visor (500 lux), a red visor (150～170 lux), and a blue visor (150～170 lux). The salivary melatonin sample, subjective sleepiness, performance of a vigilance task, and pupil size were measured. The percentage of suppression of melatonin secretion with the red visor-cap was significantly lower than that without. The red visor-cap had no negative impact on performance of the vigilance task, although the subjective sleepiness tended to increase with the red visor-cap. These results suggest that the red visor-cap can prevent melatonin suppression without a decrease in performance of the vigilance performance task.