Blue light exposure improves awareness during monotonous activities at night

Blue light used as additional lighting has been suggested to improve awareness by inhibiting secretion of melatonin hormone. However, there is still yet sufficient evidence from research. This study evaluated effectiveness of low intensity blue light to improve awareness in performing a monotonous activity at night. An experiment using within-subject design was conducted with 12 participants. They were asked to perform proof-reading activity for one hour at midnight time on two different days. The two days differed in lighting condition: regular room lighting (~150 lux) with and without additional blue light exposure. Participants´ performance was determined based on number of typographical error found in typed text. Electroencephalography (EEG) signals were recorded continuously during the experiment. Awareness was measured based on changes in (θ+α)/β of power spectral density. In addition, subjective sleepiness level was recorded using Karolinska Sleepiness Scale (KSS). Results showed that participants´ performance increased with blue light exposure. Changes in KSS level was lower with blue light exposure (0.02 vs. 0.03; p<;0.05). Evaluation of EEG signals based on (θ+α)/β also suggested that awareness was higher if blue light was utilized. In conclusion, blue light with low intensity can be used for ergonomic intervention and seems to benefit workers in enhancing awareness of clerical workers during night time.