Sleep Quality and CO₂
Tired of waking up still feeling exhausted? The culprit might be something you can't see. This is a deep dive into the surprising link between the air in your bedroom and the quality of your sleep. We'll explore what the science says about how a simple, invisible gas—carbon dioxide (CO₂)—can disrupt your rest, steal your deep sleep, and leave you with next-day brain fog. It's the simple, hidden secret to a truly restorative night.
SLEEPPERFORMANCE
Sam Kim
8/18/20253 min read
Have you ever woken up feeling groggy, even after a full eight hours of sleep? You might have the right amount of sleep, but the quality of that sleep could be compromised. While factors like noise and light are obvious culprits, there's an invisible intruder in your bedroom that could be stealing your rest: carbon dioxide (CO₂).
The culprit isn't a factory smokestack, but your own breathing! When you sleep, you exhale CO₂. In a closed, unventilated bedroom, this gas builds up overnight, turning your cozy sanctuary into a stuffy little box. Your body can sense this rise in CO₂ levels, and it’s a subtle alarm that can disrupt your sleep and leave you feeling less than stellar the next morning.
What the Science Says
Researchers have been digging into this and the findings are pretty compelling. It turns out that a buildup of CO₂ can act as a sleep thief, especially when it comes to the deepest, most restorative stages of sleep. Here's a look at what the research has uncovered:
A study from 2024 found that when people slept in a room with higher CO₂ concentrations (around 2,500 ppm), they not only had a harder time falling asleep but also experienced a significant reduction in deep sleep. The next morning, they felt sleepier and performed worse on cognitive tests. It's like their brain couldn't get the proper reset it needed overnight.
Another study from 2017 put different ventilation rates to the test. The results were clear: the worse the ventilation, the higher the CO₂ and the more fragmented the participants' sleep became. They had more awakenings and reported a lower overall sleep quality. The study concluded that simply improving air circulation is an easy way to get more restful sleep.
A 2016 study that looked at various indoor pollutants confirmed that high CO₂ concentrations were linked to more frequent arousals. These constant, tiny interruptions are enough to prevent your brain from getting the deep, rejuvenating sleep it needs.
Simply put, a poorly ventilated bedroom can sabotage your sleep without you ever knowing. The good news is, a simple fix like opening a window or using a fan to circulate fresh air can dramatically improve the quality of your sleep, helping you wake up truly refreshed.
Don't take my word for it. Follow up on the research:
"Ventilation causing an average CO₂ concentration of 1000 ppm has negative impacts on sleep" - DTU Orbit. A study from 2024 showing that CO2 levels as low as 1,000 ppm can negatively impact sleep quality, and concentrations of 1,300 ppm or higher reduce deep sleep duration.
"The Effects of Bedroom Mechanical Ventilation on Health and Sleep Quality" - AIVC. A 2017 study that found mechanical ventilation, which reduces CO2, significantly improved sleep quality and efficiency, leading to a 66% decrease in sleep movements.
"Physiological responses during exposure to carbon dioxide and bioeffluents at levels typically occurring indoors" - Saxhof Fonden Byg. A 2016 study that examined physiological responses to indoor air pollutants, including CO₂, and noted that elevated levels were associated with more frequent arousals from sleep.
Updated on August 20, 2025
While air quality plays a big role in sleep, noise can be just as disruptive. Last night I tried sleeping with the window open to improve circulation, only to discover that windows also serve an important role as sound barriers. Without them, I was kept awake by barking dogs, cars speeding by, and birds announcing the morning far too early.
Noise pollution fragments sleep much like high CO₂ does — pulling you out of deeper, restorative stages without you even realizing it. In fact, studies show that even noises you don’t consciously wake up to can still shift your brain into lighter sleep stages, lowering overall sleep quality.
Simple fixes can make a difference: silicone earplugs, white noise machines, or even heavier curtains that dampen outside sounds can all help. Tonight, I’m going to try earplugs and see how it changes my sleep quality.
Earplugs I am trying tonight:
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