People who live in areas with high air pollution are up to 60% more likely to suffer a bad night's sleep.
We know that air pollution is bad for your lungs, heart and has even been linked to dementia. Now it's also been linked to having a more restless night, in research presented at a meeting of the American Thoracic Society today.
A study of 1,863 people in the US looked at the effects on sleep of nitrogen dioxide and small particulate matter, called PM 2.5. Both are emitted by traffic and are present in high concentrations near busy roads.
The study participants' exposure to air pollution was estimated using data from Environmental Protection Agency monitoring sites and local data. It was measured at one year and five years into the study. The participants also wore a wrist monitor to measure their movements during sleep.
People who were exposed to the most nitrogen dioxide in the five-year period had a 60% increased risk of sleeping poorly. People exposed to the most PM 2.5 had an almost 50% increased risk of sleeping poorly.
The took into account the participants' age, body mass, whether they had sleep apnoea, ethnicity, income, smoking status and neighbourhood wealth.
"Prior studies have shown that air pollution impacts heart health and affects breathing and lung function, but less is known about whether air pollution affects sleep," said study author Martha Billings of the University of Washington in a statement.
It's thought that air pollution could be indirectly affecting sleep by irritating airways, causing swelling and congestion. It could also be affecting parts of the brain responsible for breathing patterns and sleep, Billings added.
The researchers stressed that this was a long-term connection, and they weren't able to tell from their data whether short-term exposure to air pollution would also be likely to disrupt sleep.
"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," said Billings.