Medical Science

Five key discoveries that have revolutionized the medical science of lighting

Discovery 1: 1980 The human circadian clock


Dr. Martin Moore-Ede, CEO of CIRCADIAN Light, led the team at Harvard Medical School that in 1980 identified the circadian clock (suprachiasmatic nucleus or SCN) in the human brain that controls our daily circadian (approximately 24-hour) rhythms of sleep and wake, body temperature and hormones. Light falls on non-visual photoreceptors in the eye and synchronizes the SCN via special visual pathways that were first traced out in rodents.

These discoveries opened up our understanding on how critical circadian rhythms were to maintaining good health and preventing sleep disruption and fatigue.

Download Dr. Moore-Ede's Original Research

Discovery 2: 1993 Blue-pump LEDs provide energy efficient lighting, but at a human cost

blue light health

In 1993 the first blue-rich LEDs went into production at the Nichia company in Japan. The 2014 Nobel prize in Physics was given to three Japanese scientists, Isamu Akasaki, Hiroshi Amano & Shuji Nakamura, “for this invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources."

The invention of Gallium Nitride LED light sources was a huge breakthrough in terms of the efficient conversion of electric power into light. Today’s highly efficient blue-rich LED lighting systems provide over 100 lumens per watt compared to only 10-15 lumens per watt from incandescent light bulbs. But this efficiency is achieved by using LED chips which primarily pump out blue light in the 440-470nm range coated with phosphors to create white light.

At the same time the technology for fluorescent lighting is improving in energy efficiency but they also emit more blue light than the transitional Edison incandescent light bulb.

Driven by concerns about climate change and global warming, energy efficient lighting is projected to replace over 50% of workplace lighting by 2020. But this comes at a significant human cost.

Discovery 3: 2001 Light exposure at night is harmful to health

blue light health

In 2001 Dr. Johnni Hansen of the Danish Cancer Society published the first major epidemiological study showing that breast cancer was increased 50% in women who worked predominantly at night. Since then hundreds of studies have identified the pathways which include suppression of the pineal hormone melatonin which normally prevents cancer tumors from growing. By 2007 light exposure on the night shift was identified as a potential carcinogen by the World Health Organization, and by 2008 Denmark started paying compensation to women who developed cancer after working the night shift.

Over the last 15 years many other diseases have been shown to be increased by extended exposure to light at night. These include obesity, diabetes and heart disease, as well as other cancers including prostate cancer in men. By 2012, sufficient data had accumulated for American Medical Association (AMA) to conclude that other diseases exacerbated by nighttime light "include obesity, diabetes, depression and mood disorders, and reproductive problems”, in addition to the "carcinogenic effects related to melatonin suppression, especially breast cancer."

In 2016 the US National Institutes of Health recognized "Shift Work at Night, Artificial Light at Night and Circadian Disruption" as a key health issue and began to explore strategies to address this serious problem before it becomes an epidemic.

Discovery 4: 2001 The circadian clock and pineal are regulated by bio-active blue light

blue light health

In 2001 Kavita Thapan, Jo Arendt and Debra Skene at the University of Surrey in England, discovered that blue light - the color of the cloudless sky – regulates the timing of our biological (“circadian”) clocks. While natural daylight, or artificial white light, is comprised of rainbow color mix of multiple wavelengths, it is predominantly the blue wavelengths that keep our circadian rhythms and sleep-wake cycle in synch with the rising and setting of the sun. In the same year, Lucas and his colleagues at Oxford University showed that the photoreceptor cells in the retina that link to the SCN circadian clock contain melanopsin, a photopigment with a peak sensitivity to 460nm blue light. The melanopsin receptors are 25 times more responsive to light at this blue wavelength than to full spectrum white light.

The problem is that the 440-470nm blue light emission spike of blue-pump LEDs in unfortunately the same wavelengths that cause maximum stimulation of the melanopsin eye receptors and the circadian clocks and pineal. Blue light is the signal which tells the circadian clock whether it is night or day.

Members of the CIRCADIAN Light team led by Dr. Robert Casper at the University of Toronto showed that filtering all light below 490nm would prevent melatonin suppression and normalize cortisol and clock genes. This helped elucidate the pathways by which light at night causes circadian clock disruption and ill health.


Thus the conventional blue-pump LEDs currently flooding the market are highly potent circadian clock disrupters and suppressors of pineal melatonin with its attendant disruptive health effects. With LED lighting projected to replace over 50% of the workplace lighting by 2020 we have an impending catastrophic collision between technological advance and human health and well-being.

Discovery 5: 2013 LEDs that do not disrupt circadian health

Early in 2013, Dr. Martin Moore-Ede and his colleagues at CIRCADIAN Light were the first to discover that LEDs with a violet pump instead of a blue pump could be used to provide safe and healthy white light at night.

In the CIRCADIAN Light Center which for the first time combined a medical research sleep lab and a lighting technology center, the CIRCADIAN team used people working 12-hour day and night shifts to probe precisely the wavelengths that had to be excluded and counter balanced them with violet light to create innovative new LED lights which protect circadian health.

Special proprietary LED chips have been designed and built by CIRCADIAN’s engineering team to optimize the circadian benefits. Today CIRCADIAN Light provides for the first time light fixtures which provide white light 24/7 but precisely control the timing of bioactive blue dosage across day and night to optimize energy and productivity and maintain good health.

The Darker Side of Light

The scientific evidence for the health risks from blue light at night. Click on links below to download publications:


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