Blue Light and How It Affects Sleep

College of DuPage Nursing Student Noah Manalo asks, “How often do you find yourself using electronic devices at night?” In today’s age, smart devices like phones, tablets, TVs, and computers are almost essential in order to get by through the day whether it’s for work or leisure. When it’s time for sleep, many of us use these devices right before we go to bed which disturbs our sleep pattern.

At night, light throws off our circadian rhythm which is our body’s biological clock. When our circadian rhythm is messed up, our sleep is disturbed. This may contribute to harmful diseases, like cancer, heart disease, diabetes, and obesity.

The culprit for this is blue light. Blue light is environmentally healthy but when it comes to sleep blue light is a problem. According to the Harvard Health Journal that reports blue wavelengths—which are beneficial during daylight hours because they boost attention, reaction times, and mood—seem to be the most disruptive at night. And the proliferation of electronics with screens, as well as energy-efficient lighting, is increasing our exposure to blue wavelengths, especially after sundown. They suggest that melatonin, while an important hormone for sleep and circadian rhythms, suppresses melatonin secretion at night and experiments are underway to investigate the relationship between lower melatonin levels and cancer.

Furthermore, the Harvard reports indicate light at night may contribute to diabetes and obesity. Researchers who observed ten people who were given a schedule, and gradually shifted the timing of their circadian rhythms demonstrated an increase in glucose levels to prediabetes and leptin levels increased. Leptin is a hormone causing a sense of fullness after eating and this hormone decreased.

The Harvard Health Letter mentions that while the light of any kind can suppress secretions of melatonin, blue light at night is the most powerful. Harvard researchers and their colleagues conducted an experiment comparing the effects of 6.5 hours of exposure to blue light to exposure to green light of comparable brightness. The blue light suppressed melatonin for about twice as long as the green light and shifted circadian rhythms by twice as much (3 hours vs. 1.5 hours).

Therefore, blue light at night or any bright light at night may be detrimental to sleep and health so exposure should be limited at night. Most smart devices have a nighttime option, which dims the blue light in the screen to a dim warm yellow. This is a good alternative to the bright light the screen produces. Another option is to stop using bright screens 2 to 3 hours before bed, or dimming screens and using warm colors like a red light. Finally, exposure to bright light in the day improves your mood and alertness during daylight, which helps boost the ability to sleep at night.


Harvard Health Publishing. “Blue Light Has a Dark Side.” Harvard Health,


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