The Effects of Blue Light on Health

Blue light is a type of visible light that is found in natural sunlight and has a wavelength of between 400 and 500 nanometers. While it is important for maintaining a healthy circadian rhythm during the day, exposure to blue light at night can disrupt the body's natural sleep-wake cycle. This is because blue light suppresses the production of the hormone melatonin, which helps regulate sleep.

In a recent study, we compared the radiation produced by smartphones when using night-mode functions or blue-light-reducing spectacle lenses. We measured the radiant flux of 64 smartphones with an integrating sphere and calculated the retinal illuminance from the radiant flux. We also measured the spectra produced by the smartphones and the transmittance of four blue-light-reducing spectacle lenses using a spectrometer.

Our results showed that night-mode functions in smartphones reduced melatonin suppression values (MSVs) by up to 93%. The warmest mode produced the least suppression. Blue-light-reducing spectacles reduced melatonin suppression by 33%, with coated lenses being more efficient than tinted lenses.

Our study found that all smartphones in our sample emit radiant power in the short-wavelength region of the visible spectrum, which may impair the regulation of circadian cycles at nighttime. We also found that the activation of night-mode functions was more effective than commercially available blue-light-reducing spectacle lenses in reducing the amount of short-wavelength light (up to 2.25 times). These findings can be extrapolated to most electronic devices, as they share the same type of white radiant sources with smartphones.

To reduce exposure to blue light and improve sleep quality, it may be helpful to use night-mode functions on electronic devices or wear blue-light-reducing spectacle lenses. By taking these steps, we can help protect our natural sleep-wake cycle and maintain good health.

For more information about this topic, be sure to check out my book, "The Sleep Thief," which goes into more detail about the effects of blue light on health and offers practical tips for improving sleep quality.

1. Teran, E., Yee-Rendon, C. M., Ortega-Salazar, J., De Gracia, P., Garcia-Romo, E., & Woods, R. L. (2020). Evaluation of two strategies for alleviating the impact on the circadian cycle of smartphone screens. Optometry and Vision Science, 97(3), 207-217.