Our environment strongly influences sleep quality; if we live in an unsafe neighborhood, we are more likely to struggle with sleep, LED streetlights can make sleep more difficult, and even wind farms have been said to harm sleep. Now we may need to add another environmental concern to the list of sleep disruptors: air pollution.
Although previous studies have found air quality in the home can affect sleep, research presented at the 2017 American Thoracic Society's International conference found that high levels of air pollution can disrupt sleep, too.
The air pollutants that may be disrupting your sleep
Researchers analyzed data from 1,863 participants and focused their attention on two of the most common air pollutants: nitrogen dioxide (NO2) and PM2.5 (fine particle pollution). Pollution data was gathered from Environmental Protection Agency monitoring sites in six U.S. cities.
By combining this data with measures from an air pollution study administered by the University of Washington, the analysis of local environment features, and the use of statistical tools, researchers were able to estimate air pollution levels in each participant’s local environment.
Measuring sleep efficiency
Data was collected on sleep and wake patterns through wrist actigraphy, and this was used to calculate sleep efficiency — a number that reflects the amount of time spent in bed asleep compared to the amount of time spent in bed awake.
For example, if you went to bed at midnight and got out of bed at 6:00 AM, but only slept for three hours, your sleep efficiency would be 50 percent. (You were in bed for six hours but were only asleep for half that time.)
Sleep efficiency is typically used when calculating an appropriate sleep schedule through sleep restriction. A healthy sleeper will typically have a sleep efficiency of around 90 percent.
How sleep efficiency is affected by air pollution
Researchers found that individuals who were exposed to the highest levels of NO2 over a period of five years were almost 60 percent more likely to have low sleep efficiency compared to those exposed to the lowest levels.
Participants who were exposed to the highest levels of PM2.5 over the same period of time were nearly 50 percent more likely to have low sleep efficiency compared to those exposed to the lowest levels of these small particulates.
Why does air pollution harm sleep?
Since NO2 and PM2.5 are both pollutants associated with road traffic, factors such as road noise and even stressful commutes may have had a negative effect on sleep.
Although this study didn’t examine why these pollutants appear to disrupt sleep, air pollution can irritate the upper airway and lead to swelling and congestion, making sleep more difficult.
As pointed out by the authors of the study, previous research has found poor air quality to impact heart health, breathing, and lung function — so taking steps to improve air quality could also improve sleep quality.