BLOOMINGTON, Ind. (AP) — The number of heart attacks among nonsmokers in Monroe County declined by more than two-thirds in the months after a countywide smoking ban took effect, according to a study by Indiana University professors.

The researchers said the results suggest smoking bans can quickly improve the health of nonsmokers as the findings in Monroe County were not matched in Delaware County, which has similar demographics but no such ban during the time of the study.

"This provides really solid evidence of the benefit of the public smoking ban, and hopefully this will provide a basis for adopting a public smoking ban in many municipalities and states," said Dong-Chul Seo, an assistant professor in IU's Department of Applied Health Science and the study's lead author.

The Monroe County ordinance prohibits workplace smoking or smoking in any indoor public place, except for some bars.

The study looked only at nonsmokers with no previous risk factors for cardiac disease.

It found of heart attacks in Monroe County dropped 70 percent — from 17 in the 22 months before the ban took effect to five in the 22 months after the ban started. The researchers found that Delaware County, which includes Muncie, saw an 11 percent drop — from 18 to 16 heart patients — for the same time period.

While the researchers concede the small number of overall heart attacks is a limitation of the study, Seo said he believes the findings are strong.

But some remain unconvinced that the smoking ban alone explains the steep drop in heart attacks.

"There could be other factors that are kind of hidden that are really driving the difference that's being seen across these counties," said Bruce Craig, director of Purdue University's statistical consulting group.

"You can certainly from these data say that there's a difference between these two counties," he said. "But you have a harder time concluding that the only reason these two counties differ is because of the smoking ban."

The researchers' conclusions, however, fit with the other studies that found an immediate decrease in heart attack rates following cigarette bans, smoking cessation experts say.

When substances in smoke enter the bloodstream, they can contribute to blockages that can result in a heart attack or stroke, said Dr. Stephen J. Jay, a professor of medicine and public health at the Indiana University School of Medicine.

"What people don't understand is that if you look at active smoking as well as passive smoking in population studies, you can see that exposure to smoke, active or passive, is perfectly capable of killing you now," Jay said.

The study was funded by the American Institutes for Research and Indiana Tobacco Prevention and Cessation published in the current issue of the Journal of Drug Education.