PhD / Lecturer of Human Physiology @ Deakin University / Interested in athlete brains / Sleep and circadian rhythms / Sport-related concussion.
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ALT Some people are way, way more sensitive to light at night than others (picture of two people near lights in the evening, lights are labeled 40 lux)
ALT You can quantify a person's sensitivity to light by looking at how quashed their melatonin rhythms are by light. Melatonin gets produced in the body as a signal for "biological night" but light exposure in the evening suppresses that production, weakening the signal
ALT Researchers at Monash University looked at the melatonin suppression that occurred when 55 people were exposed to different light brightnesses-- from four hours before normal bedtime to one hour after. On average, it only took ~25 lux to suppress half the melatonin that would have been produced in the dark
ALT But even wilder then that? The tremendous variety of responses across people tested. (Graph showing person 50x more sensitive to light) If we didn't live in a society with artificial lighting, these differences would probably be no big deal-- we wouldn't spend much of our day in those medium-low light levels. But nowadays we do. Light at night is affecting pretty much all of us, and for some, the effects are huge.
