Air pollution may be linked to higher rates of chronic kidney disease, new research suggests.
A study from the University of Michigan found the prevalence of kidney disease was greater in areas of the United States that have worse air quality.
"If air pollution is a risk factor for [kidney disease], the impact is likely to be even greater in countries where pollution levels are much higher than in the United States," study author Jennifer Bragg-Gresham, from the University of Michigan, said in an American Society of Nephrology news release.
Rates of chronic kidney disease vary widely across the United States, the researchers said. Patients' individual risk factors do not fully explain these differences, they noted.
To investigate whether air quality might have an effect on the prevalence of kidney disease, the study authors examined Medicare information from 2010 on 1.1 million Americans. They also analyzed data compiled by the U.S. Environmental Protection Agency on air quality for every county in the United States.
After taking individual risk factors -- such as age, high blood pressure and diabetes - into account, the researchers found an association between rates of chronic kidney disease and the level of a type of air pollution known as particulate matter in U.S. counties. However, they did not prove a cause-and-effect link.
The study, which was scheduled to be presented on Saturday at the American Society of Nephrology annual meeting in Philadelphia, showed the prevalence of kidney disease was higher even when pollution levels were much lower than what's generally considered unhealthy for older people and other high-risk groups.
Research presented at meetings should be viewed as preliminary until published in a peer-reviewed journal.
SOURCE: American Society of Nephrology, news release, Nov. 15, 2014