November 28, 2018
Do you crack the window at night, believing that a little fresh air will promote a good night’s sleep? You could be right.
One recent study—conducted jointly by the Eindhoven University of Technology and Utretch University of Applied Sciences, both in the Netherlands— tested 17 patients across five nights and found those who slept with the window open experienced a better rest. The reason? A lower level of carbon dioxide in the room.
But do the breezes and ambient sounds coming from the outside create ideal conditions for restorative rest? Douglas Kirsch, president of the American Academy of Sleep Medicine, and the medical director of Sleep Medicine at Atrium Health, recently told The Wall Street Journal, ““If you think about sleep evolutionarily, it makes sense that humans would prefer a physical environment that is cool and dark, like a cave.”
Kirsch generally recommends that people sleep in a room that is 65 to 68 degrees Fahrenheit and very dark. “We wake up frequently for brief periods in the night, and if there is light, we are more likely to stay up, than [to] roll over and go back to sleep,” he says.
When it comes to fresh air in the bedroom, Dr. Kirsch says that there is limited science to suggest that it improves sleep, but its impact likely depends, in part, on the external environment. A 2016 study, conducted by the Technical University of Denmark, tested how the air quality in dorm rooms impacted sleep and next-day performance. The students said that their performance was much better when the carbon dioxide was lower, thanks to an open window or the use of a fan. However, Kirsch told the journal that only the participants’ movements and their self-reported, perceived sleep quality and mental state were measured. A larger study with sensitive technical equipment would have given more quantitative results.
Indeed, Kirsch believes, if the weather is right and a bedroom window is available to open, that can be great for circulation of air, pleasant sounds of nature stirring in the morning and sunlight at dawn to align with one’s circadian rhythms.
However, in the dead of winter, in the height of summer, or in an urban setting, he says, “The draft is just not comfortable: The outdoor air will change your body temperature too much or the loud noises may disrupt sleep. Those with allergies may also be better off leaving the windows closed when the pollen count is high, especially in spring.”
He believes an alternative way to achieve a cozy sleep setting year-round is to allow for some air circulation through an open door or a fan. “There is zero scientific data that I know of, but the reason people may like fans or windows open could be the pleasant feeling of the movement of air, the cooling effect or the white noise,” Kirsch told the business news outlet.
This may explain why in certain cultures, people sleep with the bedroom window open no matter the season. “At some basic level, there is a sense of peacefulness that comes from feeling integrated with nature, which can benefit sleep,” he says. “Unless, of course, it’s freezing or there are mosquitoes or ambulance sirens to disturb you.” The comforting thought of being near nature may also explain why popular white-noise machines include settings with the sounds of birds chirping, waterfalls, and rain.
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