U.S. health experts say laws that bar smoking in public places appear to dramatically cut the number of heart attacks according to a recent study conducted by the Centers for Disease Control and Prevention.

Researchers studying a smoking ban in the western U.S. state of Colorado say a no smoking law in one city led to a 40 percent decrease in the number of residents hospitalized for heart attacks.

Dr. Terry Pechacek, with the Centers for Disease Control and Prevention's Office on Smoking and Health, says the study indicates that secondhand smoke may be an under-recognized cause of heart attack deaths.

"For too long we have considered exposure to secondhand smoke in restaurants, bars, and other places as typical and common, however, these data indicate that even brief exposure to secondhand smoke can produce rapid and adverse changes in the functioning of the heart and blood, and cause heart attacks," he said.

In 2003, the city of Pueblo, Colorado passed a law making public places and workplaces smoke-free.  Researchers say they found there were 399 hospital admissions for heart attacks in Pueblo in the 18 months before the ban.  After the no-smoking law was passed, 237 people were hospitalized for heart attacks in the same time period.

Dr. Pechacek says researchers also studied nearby areas in Colorado without smoking bans.  He says they found there was no significant change in the number of heart attack hospitalizations in these areas.  

"The fact that there was no change in the comparison counties and the comparison areas around Pueblo suggests that the only thing that is reasonable to assume as having this big effect was the impact of the law, he said.

The Centers for Disease Control and Prevention says other studies have reported that laws making public places smoke-free have led to rapid reductions in hospital admissions for heart attacks, but this is the only study that has looked at the effects over a longer period of three years.

Dr. Pechacek says he hopes the findings will lead to more laws banning public smoking in the U.S. as well as other countries.  Although, he says a World Health Organization treaty already contains a provision requiring countries to pursue protection for non-smokers from secondhand smoke.

"These data add further weight to that provision and strongly encourage that every country around the world recognize that smoking in any enclosed space is very dangerous to the non-smokers, and one of the best things we can do for public health is encourage smoke-free policies," he said.

The Centers for Disease Control and Prevention estimates that secondhand smoke exposure causes 46,000 heart disease deaths every year in the United States alone.