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. While light of any kind can suppress the secretion of melatonin, blue light at night does so more powerfully. Light at night is part of the reason so many people don't get enough sleep, says Lockley, and researchers have linked short sleep to increased risk for depression, as well as diabetes and cardiovascular problems. A mere eight lux-a level of brightness exceeded by most table lamps and about twice that of a night light-has an effect, notes Stephen Lockley, a Harvard sleep researcher. Even dim light can interfere with a person's circadian rhythm and melatonin secretion.
Light vs deep sleep full#
Their blood sugar levels increased, throwing them into a prediabetic state, and levels of leptin, a hormone that leaves people feeling full after a meal, went down.Įxposure to light suppresses the secretion of melatonin, a hormone that influences circadian rhythms. The researchers put 10 people on a schedule that gradually shifted the timing of their circadian rhythms. That's not proof that nighttime light exposure causes these conditions nor is it clear why it could be bad for us.Ī Harvard study shed a little bit of light on the possible connection to diabetes and possibly obesity. Some studies suggest a link between exposure to light at night, such as working the night shift, to diabetes, heart disease, and obesity. Charles Czeisler of Harvard Medical School showed, in 1981, that daylight keeps a person's internal clock aligned with the environment. The circadian rhythm of people who stay up late is slightly longer, while the rhythms of earlier birds fall short of 24 hours. Light and sleepĮveryone has slightly different circadian rhythms, but the average length is 24 and one-quarter hours. And the proliferation of electronics with screens, as well as energy-efficient lighting, is increasing our exposure to blue wavelengths, especially after sundown. Blue wavelengths-which are beneficial during daylight hours because they boost attention, reaction times, and mood-seem to be the most disruptive at night. Not all colors of light have the same effect. Worse, research shows that it may contribute to the causation of cancer, diabetes, heart disease, and obesity. At night, light throws the body's biological clock-the circadian rhythm-out of whack. Now, in much of the world, evenings are illuminated, and we take our easy access to all those lumens pretty much for granted.īut we may be paying a price for basking in all that light. Until the advent of artificial lighting, the sun was the major source of lighting, and people spent their evenings in (relative) darkness. What is blue light? The effect blue light has on your sleep and more.Īlthough it is environmentally friendly, blue light can affect your sleep and potentially cause disease.
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