Are Blackout Curtains Key Not Just for Sleep, But Improving Long-Term Health?

The earth is getting brighter. About 99% of people living in the United States and Europe spend their nights beneath the gleam of artificial lights, according to a 2016 report published by The New World Atlas of Artificial Night Sky Brightness. The effect is called Sky Glow—a poetic term for the cumulation of house lights and streetlights we began burning over the past century to improve our safety and productivity through the night. Unfortunately, it’s obscured the Milky Way for an estimated 80% of Americans. 

 According to two studies published this year, Sky Glow is detrimental to our sleep and long-term health. The REM-cycle disruptions spurred are linked to heart disease, obesity, and Alzheimer’s. I write this from one of the brightest cities in the world, on the most brilliant street I have ever lived on. My bedroom experience more closely resembles that of Chevy Chase’s resentful, floodlit neighbors in Christmas Vacation than it does the blackout cave our ancestors spent hundreds of millennia evolving to sleep in. According to the data, I am not alone.  

 If the insidious dangers of light pollution are alarming, the solution, on an individual, short-term level, is surprisingly simple: We need blackout curtains. “It is important to maintain as dark of a room as possible while you’re sleeping,” says Dr. Phyllis Zee, a neurologist at Northwestern University, founder of the Center for Circadian and Sleep Medicine at the Feinberg School of Medicine, and co-author of both studies mentioned above. Light is, after all, one of the most significant dictators of the body’s rhythms. This is because the retina is in direct communication with the suprachiasmatic nucleus, which is the part of the brain that schedules the release of hormones assisting in wakefulness (cortisol) and sleep (dopamine). Exposure to streetlamps or even smaller amounts of blue light, like the satisfying green glow of my air conditioner’s temperature reading, can pass through closed eyelids and trigger subtle rousing throughout the night. 

It poses a consequential threat to our health as research shows that sustained deep sleep is integral to long-term cardiovascular, metabolic, and cognitive health. “Our data and epidemiological data [shows that] having any light at night increases the risk for diabetes and hypertension in older adults,” says Zee about her most recent findings, which she co-published in Sleep this June. Meanwhile a sister paper revealed that “something like 30% of people sleep with some type of light on,” which, especially light from a television, is shown to increase the risk of obesity. In terms of cognitive health, “now we’re able to recognize that particular stages of sleep are important for removing toxic activity and molecules that develop during different parts of the day,” says Zee, likening them to exhaust produced by a car. For example, two toxic substrates flushed during slow-wave sleep include beta Amyloid and tau, protein pieces that occur in greater quantities in patients with Alzheimer’s disease. “That’s why there is a link between poor sleep and Alzheimer’s,” explains Zee.