Ireland's ban on smoking in pubs and restaurants could have added health benefits if research in the United States is anything to go by.

Nearly two years before the emerald isle became the first country to outlaw smoking in public places, the city of Helena in Montana passed similar legislation and saw a sharp drop in heart attacks.

Opponents subsequently had the U.S. law overturned but in the six months it was enforced, hospital admissions for heart attack fell by 40 percent in the city.

"The observations...suggests that smoke-free laws not only protect people from the long-term dangers of second-hand smoke but also that they may be associated with a rapid decrease in heart attacks," said Professor Stanton Glantz of the University of California, San Francisco.

Smoking is a risk factor for heart disease and stroke but Glantz's research, which is published online by the British Medical Journal Monday, is the first to report a link between a ban and heart attacks.

Only 24 people were admitted to the city's heart hospital with a heart attack during the six-month smoking ban, compared to an average of 40 during the same periods in the year before the law was imposed and after it was overturned.

Thirty-eight percent of the heart attack patients in the study were smokers, 29 percent had quit and 33 percent had never smoked.

Further studies are needed to confirm the findings but Glantz said the impact is consistent with the known effects of second-hand smoke on cardiac disease.

"The dramatic decrease in heart attacks in the Montana study makes sense because exposure to passive smoking can increase the risk of heart attack," a spokesman for the anti-smoking group ASH (Action on Smoking and Health) said.

"It all basically points to the need for a ban on smoking in public places and how crucial it is to public health," he added.

In Ireland, which introduced the nationwide ban last week, around a quarter of deaths from heart disease are caused by smoking. Smokers have twice the risk of heart attack of non-smokers.

In further research into the dangers of passive smoking also published online, pubic health experts in New Zealand discovered that people who have never smoked but who live with a smoker have a 15 percent higher risk of death than someone who resides in a smoke-free environment.

"The results from this study add to the weight of evidence of harm caused by passive smoking and support steps to reduce exposure to other people's smoke -- in the home and in other settings," Tony Blakely of Wellington School of Medicine and Health Sciences in New Zealand, said in the study.

(Agencies April 5, 2004)