Surveyed scientists stand behind current research for practical circadian lighting application

A team of researchers led by circadian lighting scientist Dr. Martin Moore-Ede has published the results of a survey, ultimately recommending broad support for implementation of lighting that positively impacts human circadian rhythms to increase human health and wellbeing.

“Fewer than 0.5% of lights sold today protect circadian health by altering their blue content across day and night,” Moore-Ede said. “Many people in the lighting industry claim that the circadian science is not sufficiently mature to incorporate into lights. So, we asked the leading scientists who work on circadian rhythms and light whether they agreed.”

The preprint publication “Lights Should Support Circadian Rhythms: Evidence-backed Scientific Consensus” was written by Moore-Ede, a former professor at Harvard Medical School and current director of the Circadian Light Research Center; Circadian senior scientist Anneke Heitmann; David Blask, professor at Tulane University School of Medicine; Sean Cain, professor at Monash University; and Randy Nelson, professor at West Virginia University.

The team collected responses from 248 scientists who have delivered more than 2,600 peer-reviewed publications on light and circadian clocks since 2008. Surveyed respondents reached consensus on 24 out of 40 test statements regarding health impacts of light on circadian rhythms.

Consensus study key points

The potential survey population comprised nearly 30,000 PubMed authors who published four or more peer-reviewed articles between April 1, 2008 and April 1, 2022. This target group ultimately narrowed down to 248 who ultimately completed the survey after opening an email invitation to participate.

The study authors devised 40 statements, 30 of which were designated “potential factual conclusions summarizing the scientific literature,” 5 were “potential practical advice conclusions about lighting,” and the remaining 5 were “potential expert policy statements based on the scientific literature.” All statements were designed with multiple choice responses indicating a range of understanding or agreement.

For the purposes of this refined group and knowledge base, and with one iteration of the survey, the investigators established consensus as 66.7%, rather than the 70–75% agreement accepted in other types of policy studies described in the paper.

LEDs notes that out of the 24 statements on which consensus was reached, survey participants reached more than 90% agreement on 10 of them:

• Robust circadian rhythms are important for maintaining good health – 95.1%
• Disrupting circadian rhythms can cause ill-health – 98.4%
• Regular daily exposure to daylight enhances circadian entrainment and strengthens circadian rhythms – 95.1%
• Increasing indoor light intensity at night increases the disruption of circadian rhythms – 90.6%
• Increasing indoor light intensity at night increases the suppression of nocturnal melatonin production – 94.6%
• The sensitivity peak of the ipRGC melanopic receptors in the human retina is approximately 480 nm in the blue part of the visible spectrum – 97.2%
• The most potent wavelengths for circadian entrainment are 460–495 nm blue light near to the sensitivity peak of the ipRGC melanopic receptors – 92.7%
• Exposure to 460–495nm blue light at night suppresses melatonin production – 90.6%
• Increasing the energy efficiency of lights is desirable, but not if it increases the risks of causing circadian disruption and serious illness – 93.2%
• There is significant variation in individual sensitivity to light, therefore circadian lighting should be optimized where possible using personalized solutions – 90.6%

Paths for industry

Overall, the authors found that “there was strong consensus that ‘there is now sufficient evidence to support the widespread introduction of circadian lighting that adjusts light intensity and blue content across day and night to maintain robust circadian entrainment and health.’” They further noted that surveyed experts agreed that “LED lights with high 460–495 nm blue content should carry the warning label ‘maybe harmful if used at night.’”

LEDs plans to follow up with further coverage on recommended steps for the lighting industry; updates on standardization efforts for circadian lighting metrics; and programs for supporting best practices and product certification.

Readers can find the full survey statements, detailed conclusions of the investigating authors, and disclosures on the Research Square website. The publication is currently undergoing peer review.

More on circadian lighting

Circadian pioneer says we’re not ready for circadian lighting. Does he really mean it?

Circadian principles require a new light language

Natural light and circadian expert blasts daylight savings

Notes on consensus statements:

Assume a range of normal indoor light intensities of 50–500 desktop lx, and assume comparable prior light exposure history

Assume a range of normal indoor light intensities of 50–500 lx, and assume comparable prior light history

Assume light bright enough (300–500 desktop lx) to read a fine-print book

CARRIE MEADOWS is managing editor of LEDs Magazine, with 20+ years’ experience in business-to-business publishing across technology markets including solid-state technology manufacturing, fiberoptic communications, machine vision, lasers and photonics, and LEDs and lighting.

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