The pros and cons of sleeping with the window open while you sleep.

For Rachel Hassard, Fall is one of her favorite seasons. But even more than football games and hot apple ciders, Hassard, 34, looks forward to Fall so she can indulge in one of her favorite comforts — sleeping with the window open.

“My apartment gets so hot, so I love having a cool breeze come in and being able to snuggle up under the blankets," she says. “It's the best."

For dozens of different reasons, sleeping with the window open can create a pleasant sleeping environment. But is it really good for your overall health? Turns out there are plenty of pros and cons to this common sleep practice.

The Pros: Deeper, More Restful Sleep

For starters, research repeatedly shows that cool temperatures make it easier to fall asleep.

Not only does cool air help you fall asleep, it helps you stay asleep, too. Sleep Number^® smart bed sleepers who describe their body temperature at night to be cold get the most restful sleep.  A 2012 study from the Journal of Physiological Anthropology found that heat exposure increases wakefulness and decreases periods of rapid eye movement sleep — in other words, the warmer the room, the harder it is to fall and stay asleep.

Additional research, like this 2015 study published in Indoor Air journal, says that open windows improve ventilation and lower the amount of carbon monoxide in a person's blood, which is associated with sleep deprivation and wakefulness.

The CONS: POSSIBLE ALLERGEN PROBLEMS

Sleeping with an open window can negatively impact your health as well. While cold air itself can't make you sick — colds and flus occur because germs overwhelm a person's immune system — it can potentially dry out nasal cavities, resulting in increased mucus production and a possible sinus infection.

In addition to dry air, sleeping with the window open can expose you to allergens that can be easily inhaled during sleep, notes Dr. Laren Tan, a pulmonologist and director of Loma Linda University Comprehensive Program for Obstructive Airway Diseases.

“Typically, we associate a high pollen count during the daytime when plants release their pollen into the air," Tan says. “But there is also evidence to suggest there are elevated concentrations of airborne pollen during the evening as well." Particularly in the spring and fall, allergens, dust, and particulate matter (such as air pollution or wildfire particulates) blow in and trigger allergies and asthma.

“Allergies and asthma can lead to more mucus production, breathlessness and increased coughing," says Tan.

And while allergies and asthma are problems in themselves, they're also conditions that can easily disrupt sleep, weakening the immune system and opening you up to other unrelated sicknesses as well.

WHAT'S THE IDEAL SLEEP TEMPERATURE? 

According to Sleep Number research, the optimum sleep environment is between 65-67 degrees. At 65 degrees, our bodies remain “thermally neutral”, meaning they don't have to do anything to create or shed heat. Body heat releases through your feet, head and hands, so keep them uncovered (or use less bedding) to stay cooler. Choose a mattress, mattress pad, pillow, sheets and other devices, such as a fan, to help keep body temperature low so you can stay asleep and stay at your best temperature for sleeping. If the room is too hot or bedding isn't breathable, heat is trapped next to you, making it difficult to get quality sleep. Avoid use of an electric blanket — it may help you fall asleep, but the extra heat will have a negative effect on your sleep during the night.

THE VERDICT

Until it's clearer how sleeping with the window open will affect your health, sleeping with the window cracked might be a better practice. Sleeping with the window open could inadvertently trigger allergies, asthma or potentially cause illness in someone with an already-weakened immune system. But for most people, it's relatively risk free. Aim to keep your bedroom around 65 degrees with 65 percent humidity. This way you aren't too cold or too warm— just the way your body likes it.

Like diet and exercise, quality sleep is essential for optimal wellbeing and performance. Because everyone's sleep needs are different, Sleep Number^® smart beds sense your movements and automatically adjust firmness, comfort and support to keep you both sleeping comfortably. Find your Sleep Number^® setting for your best possible night's sleep.