Dhaka, Sept. 24 -- You shut the windows, turn off the lights and settle down for the night. Then the coughing starts.

A cold or allergy may seem the obvious culprit. But new research suggests air pollution could also play a role.

An international study using large-scale sleep-app data has found that short-term increases in fine particulate air pollution were associated with more coughing at night.

Across 32 cities on six continents, researchers estimated that every 10 micrograms per cubic metre increase in PM2.5 was associated with a 2.4 percent rise in nighttime cough frequency in a city-specific analysis.

And the association was not confined to heavily polluted air. Researchers detected it even at relatively low PM2.5 concentrations...