The Science Behind Blue Light and Artificial Lighting

If you’ve been following me for the last few years, you’ve probably heard me talk about blue light, artificial lighting, and circadian rhythm disruption.

For most of human history, our days were guided by sunlight and darkness. But modern lighting (LEDs, fluorescents, and CFLs) means many of us spend our evenings under bright artificial lights that our biology was never designed for.

Exposure to artificial light at night can lead to:

• insomnia

• hormone imbalance

• anxiety + depression

• fatigue

• inflammation

• metabolic issues

• cancer

• impaired mitochondrial function

If you’re curious about the science behind all this, here are a few of the studies that researchers often reference when looking at how artificial light affects sleep, hormones, metabolism, and overall health.

Morning Light Helps Regulate Your Body Clock

Researchers have found that exposure to bright light in the morning helps regulate the body’s natural wake-up signals.

A study published in The Journal of Clinical Endocrinology & Metabolism found that moving from dim light to bright light in the morning triggered an immediate increase in cortisol, a hormone that helps regulate wakefulness and energy throughout the day.

Study:
Transition from Dim to Bright Light in the Morning Induces an Immediate Elevation of Cortisol Levels
https://academic.oup.com/jcem/article/86/1/151/2841140

Blue Light Can Influence Mood, Alertness, and Hormones

Another study in Chronobiology International looked at how blue-enriched light in the morning affects cognition and hormone levels.

Researchers found that morning light exposure improved alertness, reaction time, and cognitive performance, while also influencing melatonin and cortisol rhythms.

Study:
Effects of Dawn and Morning Blue Light on Daytime Cognitive Performance, Well-being, Cortisol and Melatonin Levels
https://orbi.uliege.be/bitstream/2268/171514/1/Gabel_CI_2013.pdf

Artificial Light at Night Can Disrupt Circadian Rhythms

A large literature review examining artificial light at night found that nighttime light exposure can suppress melatonin production and disrupt circadian rhythms.

Melatonin is the hormone that signals to the body that it’s time to sleep, so when it’s disrupted, sleep quality and hormonal balance can be affected.

Study:
Effects of artificial light at night on human health: A literature review of observational and experimental studies applied to exposure assessment
https://pubmed.ncbi.nlm.nih.gov/26375320/

Light Exposure While Sleeping May Affect Metabolism

A study published in PNAS found that sleeping with moderate room light increased heart rate and insulin resistance the following morning.

Even relatively low levels of light were enough to interfere with the body’s normal nighttime metabolic regulation.

Study:
Light exposure during sleep impairs cardiometabolic function
https://www.pnas.org/doi/10.1073/pnas.2113290119

Artificial Light at Night Has Been Studied in Relation to Cancer Risk

Researchers have also explored potential links between circadian disruption and cancer risk.

A global analysis examining artificial light at night found correlations between areas with higher nighttime light exposure and increased rates of certain cancers, particularly breast cancer.

Study:
Artificial Light at Night and Cancer: Global Study
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5454613/

More Research on Blue Light and Artificial Lighting

Here are a few additional articles exploring how light exposure affects human health:

• Blue light has a dark side — Harvard Health
https://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side

• Influence of the modern light environment on mood
https://www.nature.com/articles/mp201370

• Circadian clocks and breast cancer
https://breast-cancerresearch.biomedcentral.com/articles/10.1186/s13058-016-0743-z

• Blue light exposure and neurodegeneration in Drosophila
https://www.nature.com/articles/s41514-019-0038-6

Where to go from here?

If you're interested in creating a more circadian-friendly home, download my Circadian Friendly Lighting Guide, which walks through simple lighting swaps you can make to support better sleep.