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Effects of light on human circadian rhythms, sleep and mood
Blume C, Garbazza C, Spitschan M · Somnologie 23(3):147–156 · 2019
Key finding
Accessible review of how timing, intensity and spectrum of light set the clock and affect sleep.
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Entrainment of the human circadian clock to the natural light-dark cycleA week of camping without electric light shifted the internal clock ~2 h earlier and aligned it to sunrise/sunset.The new world atlas of artificial night sky brightness80% of the world and 99% of US/European populations live under light-polluted skies — the 'world is physically brighter'.Artificially lit surface of Earth at night increasing in radiance and extentSatellite data: outdoor lit area and brightness grew ~2%/year 2012–2016.Day and night light exposure are associated with psychiatric disordersBrighter days and darker nights were each independently linked to lower risk of depression and other disorders — daytime light offsets night light.Exposure to room light before bedtime suppresses melatonin onset and shortens…Ordinary room light in the hours before bed suppressed melatonin in 99% of people and shortened its duration ~90 min.
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