Unless you live in a remote mountain wilderness, far from city street lamps or a glowing laptop screen, it’s hard to find—or make—a truly dark space at night. And even if you choose an electronics-free lifestyle, you may still suffer from a night that’s too light. Most people living in the United States dwell in light-polluted areas (where artificial sky brightness is greater than 10 percent of the natural sky brightness). But in order to rest well, say experts, our bodies and brains need a sleep environment with as little artificial light as possible.

“Light signals the brain’s biological clock that it’s time to wake up. Our sleep becomes more fragmented when we’re exposed to light in our sleep,” says Lawrence Epstein, MD, author of The Harvard Medical School Guide to a Good Night’s Sleep (McGraw-Hill, 2006). Exposure to even small amounts of light during sleep (or upon waking in the middle of the night) suppresses the body’s production of melatonin, a hormone that sets your body’s internal clock and helps you sleep long enough to replenish physical and mental stores. Melatonin not only regulates the sleep-wake cycle, but also may play a role in cancer prevention. According to recent research, women living in the most heavily light-polluted neighborhoods had a surprising 73 percent higher risk of breast cancer than women in regions with less artificial lighting.

And cancer isn’t the only health risk we run: “Disruptions to that cycle can cause sleep deprivation, which in turn can lead to major health problems,” says Epstein, including weight gain, high blood pressure, chronic inflammation, and increased risk of heart disease and diabetes. Whether or not you suffer from insomnia or sleep problems, here are a few smart ways to get into the dark and stay there, for health’s sake.

Segue to slumber. At least an hour before bedtime, turn off any bright lights throughout your home. “Being in a dim environment helps set you up for sleep, which is especially important for people who have trouble dozing off at night,” says Sarah Nath Zallek, MD, neurologist at the Illinois Neurological Institute Sleep Center in Peoria, Illinois. Once you’ve turned the lights down, try unwinding with a bath, book, calming music, or gentle yoga poses. In a preliminary study published in 2008, researchers found that practicing yoga helped increase total sleep time in people with chronic insomnia.

Pull the plug. “We tend to wake up and open our eyes several times throughout the night without even realizing it,” says Zallek. “When that happens, even a little bit of light from the TV or computer can stimulate us and make us more likely to stay awake.” Even light from small items like cell phone chargers can be disruptive, she notes. But if you can’t ditch the devices altogether, at least unplug or cover up all light-emitting devices before you hit the sack. You should also turn your alarm clock away from you, or use a clock that doesn’t give off any light (such as a Zen alarm clock), recommends Zallek.

Black out the lights. At bedtime, shut off all the lights in your home. Scan your bedroom for any illuminated spots. If you notice light shining in from outside, consider investing in blackout curtains (shades made with specialized fabric that obstructs outdoor light). “Blackout curtains are also helpful for people who need or want to wake a little later, since they help you sleep right through sunrise,” says Zallek. For more help in blocking out ambient light, slip on a sleep mask or eye-pillow.

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