LOS ANGELES, Feb. 1 (UPI) -- Improvements in air quality over the past decade have resulted in fewer cases of ear infections in children, U.S. researchers suggest.
Study co-author Dr. Nina Shapiro of Mattel Children's Hospital University of California, Los Angeles, and of the David Geffen School of Medicine at UCLA and colleagues reviewed National Health Interview Survey data for 120,060 children between the years of 1997-2006.
Shapiro and colleagues measured the number of instances of frequent ear infections -- three or more within a year -- and respiratory allergy. Seizure activity, which is not influenced by air quality, was included as a control.
The data were cross-referenced with the U.S. Environmental Protection Agency's air-quality data on pollutants, including carbon monoxide, nitrous dioxide, sulfur dioxide and particulate matter, for the same time period.
The study authors discovered that as air quality steadily improved, the number of cases of frequent ear infections significantly decreased.
"We believe these findings, which demonstrate a direct correlation between air quality and ear infections, have both medical and political significance," Shapiro says in a statement.
The findings are published in Otolaryngology -- Head and Neck Surgery.