Effects of blue-enriched light on the daily course of mood, sleepiness and light perception: A field experiment

The aim of this study was to investigate the effect of blue-enriched white light on the course of mood, sleepiness and light perception over the working day in a real work setting. The participants were 30 female office workers who were divided into two groups and exposed to two light conditions (blue-enriched white light and white light) in a counterbalanced order. Mood, sleepiness and light perception were measured three times a day on 2 days of each week. More pronounced effects of blue-enriched white light on energetic arousal were found in the morning and at midday when compared to the other times of the working day. At the beginning and the end of the work day, the workers seemed to be more sensitive to the brightness of blue-enriched white light while throughout the whole work day they seemed to be similarly sensitive to colour temperature.