Poor sleep interrupted by nighttime coughing may be linked to air pollution, according to a new international study analyzing data from multiple cities around the world. Researchers from Cambridge University, in collaboration with colleagues in China and the technology company Sleep Cycle, examined coughing sounds collected over more than 500 days across 32 cities in 12 countries.

The study, published in the journal Communications Health, found a significant association between higher daily levels of air pollution and increased instances of coughing at night. Specifically, researchers observed that a rise of 10 micrograms per cubic meter in particulate matter led to an average 2.4% increase in nighttime coughing episodes.

Using passive recording technology integrated into a mobile application, the team was able to gather extensive sound data on cough frequency without active user input. This approach allowed them to assess patterns of respiratory symptoms in relation to local air quality levels.

Particulate matter, tiny airborne pollutants capable of penetrating deep into the lungs and bloodstream, is known to contribute to a range of serious health problems including heart disease and chronic respiratory conditions. The research highlights coughing as a potential early indicator of respiratory irritation or damage caused by air pollution, which may precede more persistent or chronic illness.

Dr. Tong Xia of Tsinghua University in China, a co-author of the study, noted that coughing might serve as a warning sign of underlying health issues that have not yet developed into chronic disease but could become so with ongoing exposure to pollutants. This finding underscores the importance of monitoring air quality and its impact on public health, particularly as urbanization and pollution levels continue to rise globally.