An overview of existing literature investigating effects of daytime light exposure on alertness

What is it about?

Light is known to elicit non-image forming responses, such as effects on alertness. This has been reported especially during light exposure at night. Nighttime results might not be translatable to the day. This article aims to provide an overview of (1) neural mechanisms regulating alertness, (2) ways of measuring and quantifying alertness, and (3) the current literature specifically regarding effects of different intensities of white light on various measures and correlates of alertness during daytime. In general, present literature provides inconclusive results on alerting effects of the intensity of white light during daytime, particularly for objective measures and correlates of alertness. Yet, the various research paradigms employed in earlier studies differed substantially and most studies tested only a limited set of lighting conditions. Therefore, the alerting potential of exposure to more intense white light should be investigated in a systematic, dose-dependent manner with multiple correlates of alertness, and within one experimental paradigm over the course of day.

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Why is it important?

Humans are diurnal, with optimal psychological and physiological performance during daytime. Alertness is known to affect many functions, such as performance, psychological and physiological well-being, caloric intake and pain sensitivity. Thus, displaying optimal alertness is beneficial in many facets of everyday life.