American Academy of Sleep Medicine
Why That’s Bad
It’s not just that we’re making less melatonin on our own. Light at night confuses the clocks in our body — our circadian rhythms. And circadian rhythms impact a lot more than just our sleep. Just one night of keeping the light on was found to increase nighttime heart rate, decrease heart rate variability, and increase insulin resistance the next morning in otherwise healthy adults. Unrelatedly, I’ve now set up the guest room in my house so that I can turn the lights off remotely when Walter visits.
Why That’s Bad II
Scale up a single night with too much light to a lifetime’s worth of light at night and you start to understand why people with higher sleep regularity (and more consistent light exposure) have a “20 percent to 48 percent lower risk of all-cause mortality, a 16 percent to 39 percent lower risk of cancer mortality, and a 22 percent to 57 percent lower risk of cardiometabolic mortality” than people in the most irregular sleep cohort. Regular sleep means your brain’s more confident about what time it is. Irregular sleep makes it lose confidence, which throws off rhythms all throughout your body.
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