How Air Pollution Affects Sleep Quality
A new study reveals that even in cities where air pollution levels remain below the World Health Organization's recommended daily limit, poor air quality can trigger respiratory symptoms at lower exposure levels than previously thought. This is due to the extreme sensitivity of the human respiratory system to short-term fluctuations in the concentration of fine particulate matter, even in relatively clean urban environments.
Researchers from the University of Cambridge, Tsinghua University, and Sleep Cycle found that for every 10 micrograms per cubic meter (µg/m³) increase in pollutant concentration, the frequency of coughing increased by 2.4% over the following five days.
The study analyzed cough sounds from approximately 100,000 users of the Sleep Cycle app across 32 cities in 12 countries over a period of 500 days.
“This suggests that there may not be a safe threshold for exposure to polluted air, although our study is purely observational,” said project leader Cecilia Mascolo from Cambridge.
“Nevertheless, people should consider how they can reduce their exposure to polluted air, for example, by using masks or air purifiers.”
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In addition to directly irritating the airways, nighttime coughing disrupts sleep, linking short-term exposure to polluted air with broader systemic consequences, from cardiometabolic disorders and cognitive decline to increased risks of neurodegenerative diseases associated with poor rest.
The researchers also examined the situation in Los Angeles in 2025, when the city experienced its worst wildfire season in years. They found that an increase in particulate matter concentration by 10 µg/m³ led to a 10% rise in nighttime coughing, indicating that extreme episodes of air pollution trigger immediate and disproportionately strong spikes in acute respiratory symptoms.
The authors also accounted for external factors that could contribute to increased cough levels, such as weather conditions or flu prevalence, but the characteristic pattern associated with air pollution remained.
What is the air quality level in Europe?
In 13 European cities included in the study, the average daily concentration of fine particulate matter ranged from a minimum of 5.47 µg/m³ in Uppsala (Sweden) to a maximum of 14.70 µg/m³ in Bergamo (Italy). The World Health Organization recommends that average daily exposure should not exceed 15 µg/m³ for more than 3-4 days a year.
Overall, the European cities involved in the study showed low or moderate baseline pollution levels compared to the most polluted cities in the global sample, such as Beijing at 40.97 µg/m³ or Shanghai at 33.48 µg/m³.
More Serious Health Consequences
According to the authors, in addition to simple irritation manifested as coughing and sore throat, such symptoms may indicate underlying diseases.
“We all cough from time to time, but a cough, whether a single episode or more persistent, always indicates irritation or inflammation in the lungs,” said lead author Tong Xia from Tsinghua University. “A cough may be a sign of a condition that has not yet become chronic but could become so in the future.”
