Effects of Light With Reduced Short Wavelength Components on Parameters of Circadian Rhythm and Performance in an Experimental Night Shift Model

Shift work is associated with alterations in physiological circadian patterns resulting in chronic diseases, e.g. cardiovascular disorders or major depression. The intensity and spectral composition of light is known to affect the 24 h- rhythm of our body. We investigated the effects of two different lighting environments on parameters of circadian rhythm and performance in healthy volunteers during an experimental night shift. Test light with a low color temperature was compared to normal light with a higher color temperature. Melatonin synthesis, red and white blood count, blood pressure, heart rate and indicators of performance were analyzed. Nocturnal increases in melatonin were more pronounced under low color temperature lighting conditions. This was not associated with limited degrees of arousal or vigilance. Mainte- nance of a normal nocturnal rhythm of melatonin with adapted illumination may provide a benefit for employees well- being without affecting their productivity.