We all know that a solid night’s sleep is key to waking up refreshed and ready to tackle the day. But it turns out that just hitting the sheets for the recommended 7-8 hours might not be enough. How you feel when your alarm goes off may have a lot to do with the air you breathe overnight.
A research project from Danish Technical University recently concluded that there’s a connection between bedroom air quality and brain performance the following day. In the study, researchers measured overnight bedroom air quality and sleep patterns for over 100 households in Denmark and China. The next morning, they tested participants’ cognitive abilities via a 3-minute test. The researchers found that when air quality was good, participants slept better and were more alert upon waking.
Air Quality Levels and Cognitive Performance
A common way of measuring air quality is looking at the amount of C02 in parts per million (ppm). In general, a reading of below 750 ppm indicates a well-ventilated bedroom. The higher the reading, the more likely sleep quality will be affected. For example, a reading of 1150 ppm would be typical of a bedroom with closed doors and windows and without a ventilation system (e.g. an air exchange unit). Bedroom feeling extra stuffy? Research suggests that readings above 2600 ppm will almost assuredly result in decreased sleep quality and next-day cognitive abilities.
A representative from the U.S. Environmental Protection Agency (EPA) spoke to Sleepopolis, and agrees that indoor air quality needs our attention. But they caution that “it’s important not to draw conclusions from individual studies, as different published studies vary in their results about the effect of indoor air quality on sleep, and about which pollutants are relevant.”
However, the EPA rep acknowledges, “This study is an interesting addition, as it goes a step further than most others by examining cognitive performance rather than just assessing quality of sleep. However, it shares some limitations with other studies, as noise, humidity and other factors cannot be fully controlled with open windows.”
Crack a Window for Better Ventilation
If you live in an area with low outside pollution, sleeping with an open window is a good way to increase air flow and improve quality overnight. Because an open window isn’t always an option, some consumers are turning to home air purifiers and other methods as a way to improve indoor air.
An Open Door Won’t Help
What if you can’t or don’t want to sleep with an open window? The study also looked into whether simply leaving bedroom doors open within the home contributed to better air flow and cognitive benefits. Unfortunately, the study found that, “Opening a bedroom door reduced CO2 concentration but did not provide any of the above benefits.”
Simple Ways to Improve Bedroom Air Quality
Thanks in part to SARS-CoV-2 mitigation measures, there’s been increased attention to indoor air quality in recent years. Consumer demand for air purifiers has skyrocketed and people are looking at all sorts of ways to improve the air they breathe.
Beyond opening a window, there are some actionable ways to improve air quality. Harvard Medical School suggests the following:
- Vacuum drapery and carpets and wash bedding regularly to reduce allergens like dust, pet dander, and mold.
- Skip the plants. While houseplants can add oxygen to the air, they can also harbor mold growth.
- Change filters regularly if your home uses forced air HVAC.
- Consider an air purifier and/or dehumidifier.
Additionally, the U.S. EPA representative tells Sleepopolis, “Using low-cost air pollution monitors may be a helpful complement to the traditional indoor air quality best practices of source control, ventilation, and supplemental filtration and air cleaning.”
More Research is Needed
It’s clear that in addition to increasing ventilation, we need more research into indoor air quality and its health effects. The National Institutes of Health (NIH) recently conducted a systematic review of Air Pollution Exposure and Adverse Sleep Health. 21 of the 22 articles reviewed showed a positive association between air pollution and poor sleep quality. However, despite the correlation, researchers stated it was difficult to draw conclusions due to the variances in data and study methods used in the studies. While we wait for more data, it’s not a bad idea to crack a window or use an air purifier to circulate bedroom air.
A Third of Adults Report “Always or Often” Losing Sleep Worrying About Environmental Concerns, Study Shows
ULLA JOHANNE JOHANSSON. “Ventilate your bedroom at night. You perform better the next day,” Danish Technical Institute. May 2, 2024.
Dowell D, Lindsley WG, Brooks JT. Reducing SARS-CoV-2 in Shared Indoor Air. JAMA. 2022;328(2):141–142. doi:10.1001/jama.2022.9970. June 7, 2022.
Persistence Market Research, “Air Purifier Market.” https://www.persistencemarketresearch.com/market-research/air-purifier-market.asp. 2021.
Harvard Health Publishing, “Easy ways you can improve indoor air quality,” Harvard Medical School. February 15, 2021.
United States Environmental Protection Agency, “Low–Cost Air Pollution Monitors and Indoor Air Quality,” epa.gov. 2024.
Liu J, Wu T, Liu Q, Wu S, Chen JC. Air pollution exposure and adverse sleep health across the life course: A systematic review. Environ Pollut. 2020 Jul;262:114263. doi: 10.1016/j.envpol.2020.114263. Epub 2020 Feb 24. PMID: 32443219; PMCID: PMC7877449.