We all know that pollution is bad for us and the environment, but could toxic air pollutants have even more far-reaching effects?
New research investigates the impact of air pollution on sleep quality.
The new study - presented at the American Thoracic Society (ATS) 2017 conference in Washington, D.C. - suggests that long-term exposure to high levels of pollution may lead to disrupted sleep.
The lead author of the study - Dr. Martha E. Billings, assistant professor of medicine at the University of Washington – said the research was inspired by what air pollution does to the human body.
“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,” she said. “We thought an effect was likely given that air pollution causes upper airway irritation, swelling, and congestion, and may also affect the central nervous system and brain areas that control breathing patterns and sleep.”
Air pollution and sleep continuity
Billings and her team examined data from 1,863 participants with an average age of 68 years.
The participants were enrolled in two sleep and air pollution studies as part of the Multi-Ethnic Study of Atherosclerosis (MESA).
MESA is a large-scale medical research study comprising more than 6,000 men and women from across the United States.
Billings and her colleagues investigated the effects of two common atmospheric pollutants: the traffic-related nitrogen dioxide (NO2), and PM2.5, which describes pollution comprised of inhalable particles of 2.5 micrometers in diameter or smaller.
The researchers used air pollution measurements from hundreds of locations across six cities in the United States.
Using spatio-temporal statistical models adjusted to the specifics of the cohorts, the team estimated the level of pollution at the participants’ home at two time points: one year and five years before evaluating the participants’ sleep.
As for the continuity of the sleep, the researchers used wrist actigraphy to record sleep fragmentation over seven 24-hour periods. A wrist actigraph is a commonly used device to monitor sleep parameters.
The researchers used multiple logistic regression to assess the association between traffic-related air pollution and two indicators of disrupted sleep: “low sleep efficiency” - or how much time you spend in bed awake - and “increased wake after sleep onset.”
Finally, the researchers adjusted for socio-demographic and socio-economic factors, as well as for short sleep duration and sleep apnea - a sleep-disruptive condition where a person’s breathing is interrupted when they sleep. The team also adjusted for smoking status.
Sleep trouble with high pollution exposure
The population sample was divided into quartiles - or “fourths” - depending on the levels of pollution the participants had been exposed to.
The study revealed that those in the top quartile of NO2 pollution over five years had a nearly 60 percent higher chance of having low sleep efficiency, compared with those in the lowest NO2 pollution quartile.
Additionally, those who had been exposed to the most PM5 were 50 percent more likely to have low sleep efficiency.
“There may be acute sleep effects to short-term exposure to high pollution levels as well, but we lacked the data to study that link,” Billings said. “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.”