Hiroki Noguchi

Effects of short wavelength control in polychromatic light sources on nocturnal melatonin secretion

In this study, 12 healthy males were exposed to various light conditions (2300K, 3000K, 5000K and dim) for 1.5h at midnight. The conditions of 3000K and 5000K were created by commercial fluorescent lamps. The light at 2300K was achieved by fitting a 3000K fluorescent lamp with a special filter that absorbed short-wavelength light. The vertical illuminance level was kept at 200lx. Saliva samples were taken before and after the light exposure. The light at 5000K suppressed melatonin secretion acutely. The 2300K lamp condition appeared to have no effect on melatonin secretion as well as the dim condition, while melatonin secretion was measurably suppressed by the light at 3000K.