New research has found that increased air pollution is associated with more night-time coughing, leading to disturbed sleep.
Most air pollution research looks at symptoms that are severe enough for people to seek medical help, but day-to-day symptoms can be overlooked. Prof Cecilia Mascolo, who led the study from the University of Cambridge, said: “I come from an area in Italy with very high pollution and I am very aware of its not-talked-about effects.”
Many more of us are using apps to monitor our sleep patterns. A recent survey of 18- to 30-year-olds in the UK found that 37% used sleep apps, while data from 2025 suggested that more than 40% of UK adults used tech to track their sleep.
The researchers looked at data from a commonly used sleep app. For 18 months they collected anonymised data from 32 cities in 12 countries, an average of 98,000 people a night.
As well as tracking sleep, the app also counted how many times people coughed. About half of the people coughed during the night, with 1% coughing more than 10 times. The greatest frequency of coughing was recorded in Milan and around Monza, both cities in north Italy’s Po Valley, one of the most polluted areas in western Europe.
A look at the data for Los Angeles and London shows that people cough more in cold weather and there are more coughs recorded when flu is circulating.
Mascolo said: “The hardest part was understanding if what we were seeing in the cough peaks was really affected by pollution or rather by viruses/flu trends as well as weather.”
Dr Tong Xia, part of the research team and now at Tsinghua University, added: “I thought that adding in the confounding factor of flu season would make the link in the data disappear, but it didn’t.”
High daily particle pollution was consistently associated with increased night-time coughing, but effects could also be seen at lower concentrations, well below the World Health Organization’s (WHO) air pollution guidelines.
Mascolo said: “Even in cities with relatively low levels of air pollution, such as Melbourne and Sydney, we observed positive associations between particle pollution and increased coughing.
“The LA wildfires were the clearest and most severe pollution spike in our study window.” Night-time coughing increased by 13 % during the wildfire smoke, and some people experienced effects that were delayed by several days.
Mascolo and Tong also found increased coughing in the London data around the time of Guy Fawkes fireworks and bonfires: “During the first week of November 2025, when influenza activity remained low, days with PM2.5 [particulate matter of less than 2.5 micrometres in diameter] concentrations exceeding the WHO guideline became more frequent, accompanied by a noticeably higher cough rate than previous months.
“Emission sources, such as firework displays, may have contributed to episodic air pollution and subsequent airway irritation, although source-specific data are needed to substantiate this.”
Rather than stopping action on air pollution once legal limits are met, we should be continuing to reduce air pollution.
Mascolo added: “These findings underscore the global health relevance of air pollution and suggest that the potential chronic health effects of long-term exposure to low concentrations of particle pollution warrant attention, even in comparatively less polluted cities.”
