Even Low-Level Air Pollution Linked to More Nighttime Coughing and Poor Sleep

A collaborative study by the University of Cambridge, Tsinghua University and the Sleep Cycle sleep-tracking app examined cough recordings from roughly 100,000 users in 32 cities across 12 nations over 500 days. The data show that a 10 µg/m³ increase in fine particulate matter (PM2.5) correlates with a 2.4% rise in coughing episodes during the next five days, even when daily averages stay under the World Health Organization’s 15 µg/m³ guideline.

In Los Angeles, where a severe wildfire season in 2025 pushed pollution higher, the same increase produced a 10% surge in night-time coughs, indicating a disproportionate response during extreme events. Researchers controlled for confounding factors such as temperature, humidity and influenza rates, yet the pollution-cough link persisted. The authors suggest there may be no truly safe exposure threshold and advise personal mitigation measures like masks or air filters. They also note that sleep-disrupting coughs could contribute to larger systemic risks, including cardiometabolic problems, reduced cognitive performance and heightened neurodegenerative danger.