How to assess alerting effects of daylight at the workplace? Learnings from semi-controlled studies

Daylight, in which we evolved, is naturally rich in the blue component of the spectrum and has key properties when it comes to impacts on body functioning. Current lifestyles are driving the emergence of a 24-hour society that spends most of the time indoors (around 90%), where lighting conditions are a result of design and operation priorities derived from both comfort and energy criteria, which often lead to reduced access to daylight (smaller or shaded openings) to manage solar gains and glare risks. This may result in an insufficient (day)light exposure in daily life from a physiological perspective, light being an essential cue to properly entrain our internal circadian clock and increase subjective alertness. But it is still unclear whether it can have a significant beneficial effect when compared to artificial light from a psychophysiological standpoint. Most of the studies on acute alerting effects have been conducted in well-controlled laboratory settings, where somewhat extreme and narrowly defined lighting conditions have been tested. This paper proposes assessment and monitoring techniques that would apply to semi-controlled studies instead, and focuses on the impact of daylighting in work settings by exploring ways to investigate alertness neurobehaviour and physiology in realistic indoor conditions.