Abstract
Melatonin secretion is suppressed by light exposure at night. However, little is known about the effect of moderate light exposure under an actual indoor environment on nocturnal melatonin secretion. The aim of this study is to investigate the effect of moderate light exposure in the evening on melatonin secretion. In this study, thirteen healthy males were exposed to two lighting conditions from 8:00PM to 0:00AM. One is that color temperature was 5000K (fluorescent) and vertical illuminance at eye level was kept at 100lx. Another is that there was a little light emitted from LCD display (Dim condition). Saliva samples were taken every 30 minuets during the exposure. As results, significant elevation of melatonin in Dim condition was found in about half subjects (Responders). The moderate light exposure of 100lx significantly suppressed nocturnal melatonin secretion just in Responders. Although further research is needed to find out the factors creating the difference between Responders and non-Responders, the results suggests that moderate light exposure under an actual indoor environment surely suppresses melatonin in some proportion of people.
