We have a pretty good understanding about air pollution in relation to respiratory illnesses like asthma and COPD, and know there’s a link to cardiovascular disease. But it turns out air quality also affects how well we sleep.
In 2004, the EPA awarded the University of Washington a research grant to study how air pollution affects the development of cardiovascular disease in healthy people. The Multi-Ethnic Study of Atherosclerosis (MESA) also looked for correlations between exposure to air pollution and the quality of sleep of 1,974 people in six U.S. cities: Chicago, Los Angeles, Baltimore, St. Paul, New York City and Winston- Salem.
The researchers focused on two measures of sleep quality: sleep efficiency (the total amount of time actually spent asleep) and the frequency of awakenings after falling asleep.
They compared this data set with information about the concentration of two major air pollutants around the participants’ homes: nitrogen dioxide (NO2) and fine particulate pollution (PM2.5).
NO2 forms when fossil fuels (coal, oil, gas, diesel) are burned at high temperatures. Common sources of PM2.5s are motor vehicles, airplanes, wood burning (residential and forest fires) and dust storms.
The researchers took this information from the EPA’s monitoring sites similar to the monitors we have in Utah’s non-attainment areas (areas where air quality fails to meet the standards set by EPA).
When the original study was completed in 2014, initial findings showed there was about a 60% decrease in sleep efficiency if you had exposure to more air pollutants. The higher the concentration of indoor air pollution, the greater the number of people experiencing poor quality sleep—and less of it.
Because the study was not a randomized controlled trial, the results found an association, not a cause-and-effect relationship, between air pollution levels and sleep quality. The researchers don’t exactly know how air pollution may affect sleep, but there are many possible mechanisms in which air pollution could be causing people to toss and turn.
Researchers also found that since exposure to air pollution affects upper airways with respiratory illness and inflammation, it could lead to an increase in sleep apnea. Sleep apnea is a potentially serious sleep disorder in which breathing repeatedly stops and starts during sleep. Obstructive sleep apnea is the more common type, occurring when the throat closes and blocks the flow of air. An estimated 22 million Americans live with this condition, according to the American Sleep Apnea Association.
In a followup study, published last year, the link between air pollution and sleep apnea remained, even after the researchers took into account other factors that could have affected the results like body mass index, high blood pressure, diabetes and smoking.
Potential allergens such as pollen, mold spores and dust can also increase symptoms of sleep apnea. Indoor and outdoor pollution can damage the mucous membranes of the nose and throat, so some doctors think there’s a link between nasal congestion and sleep apnea, but most agree that further study will have to be done to find conclusive evidence.
The study found a participant’s odds of having sleep apnea increased by:
- 60% for each five micrograms per cubic meter increase in yearly PM2.5 exposure
- 39% for each 10 parts per billion increase in yearly NO2
Air quality improvements may have an unrecognized benefit, the researchers summarized: better sleep and better health
Next month CATALYST will address how to improve your indoor environment.
In the meantime, think of a good night’s rest each time you choose to:
turn off your engine instead of idling;
trip-chain your tasks while the car engine is warm;
take public transit;
honor a no-burn day;
turn down the thermostat…
You know the drill by now.
Studies are starting to prove what is, after all, logical: Whether it’s inside or outside of our bodies, cleaner air means a better quality of life for all.
Ashley Miller, J.D., is the vice-chair of Breathe Utah. She is the vice-chair of Utah’s Air Quality Policy Advisory Board and a member of the Salt Lake County Environmental Quality Advisory Commission.