Sleeping with the windows open has been a long common practice, especially on warm summer nights or pleasantly cool fall evenings. Even medical professionals throughout history have long advocated for getting fresh air as a way to improve your health.
But what about the science about the positive impact of fresh air on the health of our sleep?
In order to understand the extent of the benefits, we’ve enlisted the help of sleep experts to weigh the pros and cons of sleeping in fresh air, the science behind the phenomenon, and what you should know before leaving your windows open overnight.
How Does Fresh Air at Bedtime Benefit the Brain and Body?
1. It may lower your risk for developing allergies and contracting diseases
According to sleep specialist and neuroscientist Dr. Chelsie Rohrscheib, breathing properly is essential for staying healthy and getting proper sleep.
“Poor air quality can increase your risk of developing allergies and certain diseases such as asthma, or respiratory infections such as colds, the flu, bronchitis, COVID-19 and pneumonia,” she explains.
2. It may increase your oxygenation levels and overall sleep quality
One of the easiest ways to improve air quality in your bedroom is to allow fresh air to circulate through. This increases oxygen levels in your blood, Rohrscheib says, which then increases the overall quality of sleep.
“People with proper breathing experience deeper, more refreshing sleep, are able to fall asleep faster, and are less likely to experience nighttime awakenings,” she adds.
A 2015 study tested the impact of bedroom ventilation through two experiments, with one using an open window and the other using a fan. The fan would turn on when CO2 levels exceeded a certain amount (thus signaling a need for more oxygen). The study found that lower CO2 levels — which can be due to open windows or fans — resulted in increased perceived freshness of bedroom air, as well as an improved ability to concentrate and perform the next day.
3. It helps you wake up less at night
“If air quality is low, and breathing is poor, you may wake up several times per night,” Rohrscheib says. “This can keep you from entering the deepest, most refreshing stages of sleep, leaving you feeling tired the next day.”
Our brains perform better when there’s more oxygen. “Since the brain remains active during sleep by processing information, it requires oxygen,” says Alex Savy, certified sleep science coach. “Sleeping with your window open can give the brain its oxygen ‘boost,’ which would allow it to process the information easier and, potentially, let you sleep more soundly while it’s busy doing its job.”
Is There Such a Thing As an Unhealthy Amount of “Fresh” Air?
Rohrscheib notes that people with allergies should be mindful of open windows during spring and summer months, when plant pollen is at its highest level. There’s also the risk that outside air quality could be worse than air quality inside of your home, particularly if you live in an area with high pollen counts or automobile traffic. To check pollen levels around you, pollen.com or weather.com are great resources.
On colder nights, Savy explains that keeping your bedroom window open may help you fall asleep faster. “Fresh air can cool you down,” he says. “Because our body lowers its core temperature when sleeping, cooling down using fresh air can help you achieve the needed core temperature faster and consequently, fall asleep faster.”
However being aware of your body temperature is essential. Savy notes that it's smart to keep a warm blanket nearby, just in case. Consistently low body temperatures may lower your body's immune response and make you more susceptible to an infection via germs.
Are There Alternatives to Opening Your Window for Fresh Air?
If you can’t open your window, due to air quality, noise, or other reasons, you may want to consider investing in a fan or air purifier. While Rohrscheib cautions that air purifiers can’t completely replicate fresh air, she shares that they can still provide some level of benefits.
“They do help reduce pollutants, dust, and allergens in the environment,” she explains. “If you have allergies or a breathing disorder, air purifiers can help improve the quality of the air and keep your breathing condition from getting worse.” Being able to breathe better, Rohrscheib explains, can play a vital role in a person’s quality of sleep.
Aim for Fresh Air Whenever You Can Get It, Not Just at Night
If keeping the windows open isn’t ideal for you, your sleep can still benefit from fresh air. Plan to spend time outdoors before bed. Some studies show that just 20 minutes in nature can help relieve stress — a mental barrier that prevents many from falling asleep a night — which could lead to quicker sleep.
If you're able to get outside in the morning or while the sun is out, that sun exposure will play an important part in regulating your circadian rhythm, which then regulates your sleep cycle.
“Fresh air at any time of the day is a positive [thing],” says sleep expert and neurologist Dr. Pietro Luca Ratti. “Fresh air has a way of making us feel calm and tired, so if you are able to spend a long time outdoors during the day, then you should feel more tired by the time you go to bed.”
Think of fresh air as a holistic tool and get it when you can. “Fresh air is like water,” Ratti says. “It’s always a good thing.”
How to Track if Fresh Air Is What You Really Need
To track if fresh air is making a difference in your quality of sleep, you might want to keep a sleep diary. For two weeks, track the time it takes to fall asleep and how you feel the next day, whether it’s by gauging the energy you have when you wake up, your exercise performance, or how productive you are at work.
During spring and summer months, you may also want to track if your allergies have gotten worse or better when you leave the windows open at night. While fresh air can improve our immune system through better quality air and sounder sleep, the quality of air is very location-specific. You may want to invest in an air purifier during pollen-heavy months to avoid allergies and the disrupted sleep allergies can cause.
There are also practical reasons for not opening your window at night. Beyond air pollution or pollination, which we mentioned above, the location of your window may not be ideal, due to noise, safety, or critters.
Which is why it’s important to remember that fresh air is more of a sleep experience enhancement than a sleep requirement. In fact, Rohrscheib cautions against using fresh air as a solution for more serious sleep concerns, and recommends that concerns about underlying causes should be routed to a medical professional first. There may be solutions your doctor recommends that solve your sleep problems
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