Light, entrainment and alertness: A case study in offices

It is well established that light affects both visual and non-visual systems. Laboratory studies have shown that, depending upon the time of exposure, short-wavelength light of sufficient amount and exposure duration will either entrain or disrupt the synchrony between our biological clock and our local position on Earth. Laboratory studies have also shown that light across the entire visible spectrum can enhance alertness, both day and night. Scant attention has been given to testing the effects of light on building occupants’ non-visual responses, and, consequently, lighting specifiers have been offered little guidance on the design and application of lighting for non-visual effects. The present study helps to fill that gap through field-testing of light exposures from a novel luminaire designed to promote entrainment and alertness throughout the day in actual office environments. The data support the inference that light exposures, when properly applied, can promote circadian entrainment and increase alertness.