LIGHT AND HEALTH
ARE CODES AND STANDARDS
OBSTACLES TO
Circadian-Effective Lighting Design?
By JENNIFER BRONS AND DAVID PEDLER Light and Health Research Center at Mount Sinai
Humans are a day-active species. Regardless of where we live on Earth, most of us wake up in the morning, eat and work through the brightness of the day, return home to dial things down a notch in the evening, and sleep through the dark night. This cycle is governed by circadian rhythms that are generated and regulated by the central brain’s master biological clock, which uses the pattern of light received by the retina to synchronize the body’s various functions to do the right things at the right time. People who habitually disrupt this pattern by exposure to only dim light during the day or bright light at night are at risk for a host of health conditions 20
designing lighting
like cancer, metabolic and cardiovascular diseases, and mental health disturbances like anxiety and depression. LHRC researchers have long explored and measured the relationship between light and the human circadian system for promoting health and well-being (see the August 2025 issue). To that end, we developed an empirical model1-3 that quantifies how light at the retina is converted into neural signals for the master clock. The model employs a metric called circadian stimulus (CS) that accounts for factors such as a light exposure’s duration, level, and spectrum as well as the timing and history of