A smoking ban in one Colorado city led to a dramatic drop in heart attack hospitalizations within three years, a sign of just how serious a health threat secondhand smoke is, government researchers said. The study, the longest-running of its kind, showed the rate of hospitalized cases dropped 41 percent in the three years after the ban of workplace smoking in Pueblo, Colo.,

took effect. There was no such drop in two neighboring areas, and researchers believe it's a clear sign the ban was responsible.

The study suggests that secondhand smoke may be a terrible and under-recognized cause of heart attack deaths in this country.

At least eight earlier studies have linked smoking bans to decreased heart attacks, but none ran as long as three years. The new study looked at heart attack hospitalizations for three years following the July 1, 2003 enactment of Pueblo's ban, and found declines as great or greater than those in earlier research.