Strategies for Delivering Circadian Stimulus in a Classroom While Minimizing Energy Use

This article builds upon a previous article in LD+A that presented strategies for delivering circadi-an-effective light in an office space while minimizing energy use. While various methods for defining circadian-effective light have been proposed, we chose the circadian stimulus (CS) metric J because our work is based on the scientific literature showing that rods, cones and intrinsically photosensitive retinal ganglion cells (ipRGCs) participate in how the retina converts light signals into electrical signals for the master biological clock. The CS metric is derived from circadian light (CLA 2.0), which characterizes the spectral sensitivity of the circadian phototransduction circuits in the human retina.12 Reflecting the circuits' operating characteristics, from threshold to saturation, CS is therefore postulated as a measure of the effectiveness of optical radiation incident on the retina for stimulating the biological clock. LHRC laboratory and field studies have shown that exposure to a CS of 0.3 or greater for at least two hours per day, especially in the morning, is effective for improving sleep quality, mood, and alertness and reducing stress in office workers,3 as well as for reducing depression in people with Alzheimer's disease and related dementias living in long-term care facilities.