Increases in sleep problems were linked with increases in short-term outdoor temperatures all year long and with increases in the pollution levels during summer months.
How much? In the summer, she says, ''you are at a 13% higher risk of having shallow breathing or stopping breathing for at least 10 seconds if pollution goes from the lower range to the higher range of pollution for that city."
''This is clinically significant," she says, with people likely to notice the effects on sleep quality.
While the study finds a novel link between pollution and sleep problems, there are unanswered questions, Gold says. ''How much of the cardiac risk that can be explained by pollution, we don't know yet."
Or the particles may adversely affect the upper airways. "You could have upper airway inflammation from pollution," Gold says.
The findings may come as a surprise to many experts, says John Heffner, MD, past president of the American Thoracic Society and William J. Garnjobst Chair of Medical Education, Providence Portland Medical Center, Portland, Ore. He reviewed the study findings for WebMD.
The study findings add on to a body of information that's well accepted, Heffner says. "We know that air pollution is a risk factor for cardiovascular disease by itself," he says. It's also known that sleep-disordered breathing is associated with cardiovascular disease.
''We need more research to see if there is really a causal link [between pollution and sleep-disordered breathing]," he says. The new study found just an association, not cause and effect.
Even so, those who know they have sleep breathing problems can take precautions, Heffner says.
"I would advise patients with sleep-disordered breathing, particularly if they are not too responsive to therapy for their sleep problems, to seek air conditioned homes, and to seek out air conditioning if they don't have it in their homes during times of serious air pollution problems."