When we think of air pollution, we often imagine smog in the skies, carbon monoxide gas emitted from vehicles, smoky sulfur dioxide near factories or some other way toxins negatively impact our environment.
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But air pollution isn’t just harmful to our surroundings — atmospheric substances can have damaging effects on humans (and other living things, too).
In fact, according to the World Health Organization, air pollution alone is responsible for 7 million deaths a year.
And now, researchers say pollutants can be the cause of poor sleep.
The new study, presented at the American Thoracic Society's annual international conference Sunday, showed high levels of pollution over time could affect sleep quality.
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Researchers from Harvard University, Columbia University, University of Washington and Brigham and Women’s Hospital analyzed data from 1,863 participants, adjusting for factors such as age, body mass, sleep apnea, smoking status and more.
They then collected five years’ worth of pollution data in the six U.S. cities where the participants lived and measured two of the most common air pollutants, nitrogen oxide (traffic-related pollutant) and fine-particle pollutants.
For seven days, the team analyzed participants’ sleeping patterns and used wrist actigraphy, a watch-like device that measures small movements, to calculate “sleep efficiency” or the percentage of time in bed spent awake compared to time spent asleep.
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What the researchers found was that the group with the highest levels of nitrogen oxide over five years were nearly 60 percent more likely to have poor sleeping habits (or sleep efficiency) compared to the group with the lowest nitrogen oxide levels.
Similarly, the group with the highest exposure to fine particles had about a 50 percent increased likelihood of low sleep efficiency.
The team also found participants who were exposed to more air pollution spent more hours awake.
"These new findings indicate the possibility that commonly experienced levels of air pollution not only affect heart and lung disease, but also sleep quality. Improving air quality may be one way to enhance sleep health and perhaps reduce health disparities," lead author Martha E. Billings said.
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Future research, she added, should explore the mechanisms by which pollutants like the ones studied disrupt sleep patterns.
More about the full study at thoracic.org.