The Harvard Health Letter, a news website maintained by Harvard Medical School, published an article in August 2018 entitled “Blue Light Has A Dark Side.” It explained that exposure to blue light at night affects the quality of sleep of involved individuals because it suppresses the natural secretion of melatonin. Disrupted sleep has been linked to numerous health problems.
Melatonin is a hormone released primarily by the pineal gland that regulates the sleep-wake cycle. Melatonin supplements have also been marketed as a short-term treatment for individuals having trouble sleeping due to jet lag or shift work. A disturbance in the natural secretion of this hormone leads to a disrupted circadian rhythm or biological clock.
Note that there are different sources of blue light. The most notable ones are the twisted nematic or TN and in-plane switching or IPS LCD and OLED display panels. Other notable sources are the white variants fluorescent lamps and LED lamps, that produce visible light within the blue spectrum. Natural sunlight also has a relatively high spectral density of blue light.
Explaining the Purported Negative Health Effects of Blue Light Exposure
The Harvard Health Letter referenced two studies to explain how blue light affects individuals. One study conducted by Harvard researchers and their colleagues revealed that blue light exposure suppresses melatonin for about twice as long and shifted the circadian rhythms by twice as much as exposure to green light.
Another study by researchers from the University of Toronto involved comparing the melatonin levels of two groups of people: one exposed to bright indoor light while wearing goggles that blocked blue light and the other one exposed to regularly dimmed light without wearing goggles. Findings revealed similar melatonin levels between the two groups.
The study of A. M. Chang, D. Aeschbach, J. F. Duffy, and C. A. Czeisler revealed that people who read on devices took longer to fall asleep, had less REM sleep, and had higher alertness levels before bedtime than those who read printed books. Furthermore, those who read on devices took longer to wake up and were sleepier.
Blue light exposure can also damage the eyes according to other studies. A review by G. Tosini, I. Ferguson, and K. Tsubota noted that such exposure, particularly coming from LED lamps, could induce photoreceptor damage. However, the same study recommended the use of LED lamps with an emission peak of around 470 to 480 nm.
A laboratory experiment by K. Ratnayake et al. examines the link between blue light exposure and macular degeneration. It revealed that light triggers a chemical reaction in a molecule called retinal within photoreceptor cells. This reaction generates harmful substances that can destroy these cells and potentially contribute to age-related macular degeneration.
Blue light is particularly harmful because it occupies the high-energy end of the visible light spectrum. This borders on the ultraviolet range. It also carries more energy per photon compared to lower-energy colors like red or green. This heightened energy makes it more likely to damage cellular structures when absorbed by tissues in the body.
Arguments Against the Supposed Negative Health Effects of Blue Light
David Ramey, a specialist in retinal disease and surgery, wrote an article for the Harvard Health Blog to discuss the health implications of blue light exposure. He explained that high-intensity blue light from any source is potentially damaging to the eyes. He added further that looking directly at the point of high-powered LED lamps is potentially dangerous.
However, while cautioning people about the risks of extremely bright blue light, Ramey also clarified that blue light emitted by popular consumer electronic devices like smartphones, tablets, and computer screens is less intense than high-powered sources and unlikely to significantly increase the risk of eye conditions like macular degeneration or blindness.
Exposure to specific lower-end wavelengths of blue light can also be beneficial according to a review by C. Chao, Y. Zhou, G. Tan, and J. Li. The researchers noted that this exposure has a role in regulating the circadian rhythm by aiding the secretion of melatonin during the daytime. Blue light can also promote human eye refractive development.
Tech companies like Apple, Google, and Microsoft have included so-called dark mode or night shift features for reducing blue light emissions in their consumer electronic products. These features enable users to manually or automatically shift the color temperature and tone of their display screens toward warmer hues to reduce eyestrain.
However, because of the shift in color temperature, there is a growing disagreement about this approach. The features can impact both the user interface and user experience. A shift to warmer hues affects color reproduction accuracy. Some have noted that eyestrain results from prolonged periods of using the eyes and not from exposure to blue light.
It is illegal for ophthalmologists, optometrists, and other health care practitioners in the United Kingdom to tell patients that blue light within the 400-450 nm range can negatively affect sleep and cause health effects. The U.K. Advertising Standards Authority fined Boots Optician in 2017 for claiming that its blue-light-filtering lenses can prevent eye diseases.
Summary and Takeaway: How Does Blue Light Affect Health
The verdict about the negative health effects of blue light exposure is considerably simple. Studies have shown that such exposure from using electronic devices or lighting fixtures at nighttime can indeed affect melatonin secretion and disrupt the biological clock. Disrupted sleep has been linked to physical and mental health problems. However, no studies indicate that exposure to similar sources could result in eye damage.
FURTHER READINGS AND REFERENCES
- Chang, A. M., Aeschbach, D., Duffy, J. F., and Czeisler, C. A. 2015. “Evening Use of Light-Emitting eReaders Negatively Affects Sleep, Circadian Timing, and Next-Morning Alertness.” PNAS. 112(4): 1232-1237. DOI: 10.1073/pnas.1418490112
- Chao, Z. C., Zhou, Y., Tan, G., and Li, J. 2018. “Research Progress About the Effect and Prevention of Blue Light on Eyes.” International Journal of Ophthalmology. 11(12): 1999-2003. DOI: 10.18240/ijo.2018.12.20
- Harvard Health Publishing. 2018, August 13. “Blue Light Has A Dark Side,” Harvard Health Letter. Harvard Health Publishing. Available online
- Ramsey, D. 2019, April 8. “Will Blue Light from Electronic Devices Increase My Risk of Macular Degeneration and Blindness?” Harvard Health Blog. Harvard Health Publishing. Available online
- Ratnayake, K., Payton, J. L., Lakmal, O. H., and Karunarathne, A. 2018. “Blue Light Excited Retinal Intercepts Cellular Signaling.” Scientific Reports. 8(1). DOI: 10.1038/s41598-018-28254-8
- Tosini, G., Ferguson, I., and Tsubota, K. 2016. “Effects of Blue Light on the Circadian System and Eye Physiology.” Molecular Vision. 22: 61-72. PMID: 26900325
- Woodley, M. 2015, May 31. “Optical Chain Fined $69,000 for Misleading Ad.” Insight. Available online