Impact of weekly lighting condition on performance, sleepiness, and mood

Abstract

It was hypothesized that lack of daytime circadian stimulus (dim light) would delay circadian phase from the start to the end of the week, resulting in a greater decrement in performance and mood as well as an increase in sleepiness at the end of the week. Results show reduced sleepiness in high CS lighting conditions, but this effect was not increased over the course of the week. The impact of the dim light condition on performance is less clear showing limited evidence of the chronic impact of light deprivation on performance. Reaction time results indicate a more acute than chronic impact, while accuracy measures show a trend toward a greater decrement over the course of the week when subjects were deprived from daytime circadian light, but this difference did not reach significance. Memory measures do not show any significant changes due to lighting condition. Mood remained slightly better over the week in daylight than in dim light. Self-reported sleep duration increased over the course of the week. Overall results clearly indicate reduced sleepiness and a slight maintenance of mood, but the impact of daytime light on performance remains elusive.