Air pollution may be disrupting sleep at levels far lower than expected. While colds, dry air, and allergies are common reasons for nighttime coughing, researchers are investigating whether poor air quality, often invisible to the naked eye, plays a role in these interruptions.
Tracking Coughs With Smartphones
A new study used data from a popular sleep-tracking app to investigate the link. Researchers from the University of Cambridge, Tsinghua University, and the company Sleep Cycle analyzed microphone recordings from tens of thousands of users across 32 cities in 12 countries.
The team gathered roughly 500 days of anonymized data. They then compared these findings with daily PM2.5 levels in each city. PM2.5 refers to particulate matter smaller than 2.5 micrometers, which can travel deep into the lungs and is linked to inflammation and cardiovascular issues.
The researchers also controlled for variables such as weather and influenza activity. This helped them determine if changes in air quality were influencing coughing patterns beyond other factors.
The Data Shows a Clear Pattern
The study found a consistent relationship between air quality and respiratory responses. For every 10 microgram-per-cubic-meter increase in PM2.5, nighttime coughing increased by about 2.4%. This correlation appeared even when pollution levels remained below World Health Organization guidelines.
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The researchers noted that the connection held during real-world events. In Los Angeles, which was included in the study, PM2.5 levels rose sharply during wildfires in January 2025. Nighttime coughing increased alongside those rising levels.
Because the study observed these patterns across a large population, the findings suggest that our bodies may react to changes in air quality on a shorter timeline than previously thought. While the research cannot prove causation, the consistency of the results strengthens the argument that poor air quality can trigger respiratory issues quickly.
For individuals living in areas with frequent pollution spikes, this means the air quality at the end of the day can still impact sleep quality. When the lungs are inflamed from exposure, the body’s natural response is to cough, which can fragment sleep cycles and reduce overall restfulness.
Reducing Indoor Pollution
While people cannot control the air outside, they can take steps to limit exposure indoors. Checking the Air Quality Index (AQI) before heading out provides a quick snapshot of daily conditions.