What Can You Do About This?
Not everyone’s melatonin is affected by nighttime light to the same degree. “Some people are very much sensitive to very dim light, whereas others are not as sensitive and need far, far more light stimulation [to impact melatonin],” Benedict said. In one study, some volunteers needed 350 lux to lower their melatonin by half. For such people, flipping on the light in the bathroom at night wouldn’t matter; for others, though, a mere 6 lux was already as harmful – which is darker than twilight.
You can protect yourself by keeping your bedroom lights off and your screens stashed away, but avoiding outdoor light pollution may be harder. You can invest in high-quality blackout curtains, of course, although some light may still seep inside. You can plant trees in front of your windows, reorient any motion-detector lights, and even petition your local government to reduce over-illumination of buildings and to choose better streetlights. You can support organizations, such as the International Dark-Sky Association, that work to preserve darkness.
Last but not least, you might want to change your habits. If you live in a particularly light-polluted area, such as the District of Columbia, America’s top place for urban blaze, you might reconsider late-night walks or drives around the neighborhood. Instead, Hanifin said, read a book in bed, while keeping the light “as dim as you can.” It’s “a much better idea versus being outside in midtown Manhattan,” he said. According to recent recommendations published by Hanifin and his colleagues, when you sleep, there should be no more than 1 lux of illumination at the level of your eyes — about as much as you’d get from having a lit candle 1 meter away.
And if we manage to preserve outdoor darkness, and the stars reappear (including the breathtaking Milky Way), we could reap more benefits — some research suggests that stargazing can elicit positive emotions, a sense of personal growth, and “a variety of transcendent thoughts and experiences.”
A version of this article appeared on WebMD.com.