Lighting Research Center Lighting Research Center
Light & Health

Researching how light can be used to promote health and wellbeing

Biological rhythms that repeat approximately every 24 hours are called circadian rhythms. Light is the main stimulus that helps the circadian clock, and thus circadian rhythms, keep a synchronized rhythm with the 24-hour day. If lack of synchrony or circadian disruption occurs, we may experience decrements in physiological functions, neurobehavioral performance, and sleep.

Lighting characteristics that are effective to the circadian system are different than those effective to the visual system. In order to apply light to mitigate symptoms of Alzheimer's disease, depression, jet lag, or sleep deprivation, we need a better understanding of the quantity, spectrum, timing, duration, and distribution of light that is effective for the circadian system.

Educational videos

Sponsored by the Light and Health Alliance and the National Institute for Occupational Safety and Health (NIOSH), Grant 1R01OH010668, the LRC has created a series of brief videos that explain the human circadian system and circadian light. Click image to watch the video on YouTube.

1. Circadian Rhythms. Dr. Mariana Figueiro gives a brief overview of human circadian rhythms, why they’re important, and the need for staying entrained with lighting. circadian rhythms video
2. Circadian Stimulus. Dr. Figueiro gives a brief overview of circadian stimulus (CS), a metric developed at the Lighting Research Center to quantify the extent to which lighting impacts the human circadian system. She discusses the role that light levels and spectrum play in CS, the impact of other qualities of lighting, and other metrics that are talked about but don’t predict light’s effect on the circadian system. circadian stimulus video
3. How to Use the LRC's Circadian Stimulus Calculator. Dr. Figueiro gives an overview of the LRC’s circadian stimulus calculator, which quantifies CS provided by one or more light sources. The calculator is available at Calculator video

Circadian stimulus calculator

calculatorThe LRC has released a web-based version of its CS calculator with more robust and flexible functionality to help lighting professionals select light sources and light levels that will increase the potential for circadian-effective light exposure in architectural spaces. This calculator provides additional functionality not included in earlier versions. (Release date: March 12, 2018)



Download Excel-based Calculator for off-line use. [Multiple Light Sources] Compatible with Mac and Microsoft Excel 2010 or later. Clicking this link will directly download a Microsoft Excel file to your computer or other device. Users should click "Enable Macros" upon opening the file. (Updated 10/3/2017.)

Circadian stimulus look-up charts

These look-up charts provide a quick and easy way to estimate the potential average CS value in a space using conventional lighting metrics.

Lighting Patterns for Healthy Buildings

Lighting Patterns for Healthy BuildingsThe website, Lighting Patterns for Healthy Buildings, assists lighting designers and specifiers in selecting quality lighting that supports healthy living. Designed in the spirit of traditional architectural pattern books, it presents model designs for typical rooms that can be adapted to specific buildings and styles.

The patterns are based upon the 24-hour lighting scheme for older adults proposed by Mariana Figueiro in 2008, which recommends cycled electric lighting with cool, high light levels for high circadian stimulation during the daytime, and warm, low light levels for reduced circadian stimulation in the evening, along with good lighting for visibility, and nightlights to provide horizontal/vertical cues to improve postural control and stability.

This website allows users to view lighting patterns showing base case and new lighting design analyzed for circadian stimulus (CS). Each pattern presents lighting plans, renderings, and generic luminaire information useful for providing healthy lighting throughout the day.

LD+A Article "Designing with Circadian Stimulus"

This article provides a basic introduction to designing with the CS metric. In the article, LRC researchers explain the metric and present useful tips to help designers create lighting plans that deliver prescribed amounts of CS. The article is available here.

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