Sept. 21, 2009 -- Smoking bans cut heart attacks, two separate studies show.

Each of the studies combined data from all previous studies of the effects of smoking bans on heart attacks.

Each came up with the same finding: Overall, smoking bans cut heart attacks by 17% -- and this effect increases over time. There's a 26% drop in heart attacks each year after smoking bans are in effect, one of the studies calculates.

This reduction in risk "is not trivial," notes an editorial by Steven A. Schroeder, MD, of the University of California, San Francisco.

"Secondhand smoke exposure is nearly as harmful to the heart as is chronic active smoking," Schroeder writes. "It is prudent to assume that exposure to secondhand smoke is almost as dangerous to persons with diagnosed or latent coronary disease as active smoking."

Exactly what can breathing in the smoke from someone else's cigarette do to you? It can:

Make the blood sticky and more prone to clotting

Stiffen the arteries

Disrupt crucial functions of the arteries

Decrease good HDL cholesterol

Stimulate inflammation

Make heart attacks worse

Increase damage from free radicals

Increase risk of heart rhythm problems

Increase insulin resistance

"It is hard to imagine substances that would be more cardiotoxic," Schroeder suggests. "Furthermore, these adverse effects are observed at very low exposures."

It doesn't take long for smoking bans to show results, notes David G. Meyers, MD, MPH, of the University of Kansas, lead author of one of the studies.

"The beneficial effect of smoking bans seems to be rapid, with declines in [heart attacks] within three months," Meyers and colleagues report.

The findings make a strong argument for smoking bans, suggests James M. Lightwood, PhD, co-author of the second study.

"Passing 100 percent smoke-free laws in all workplaces and public places is something we can do to protect the public," Lightwood says in a news release. "Now we have a better understanding of how you can predict what will happen if you impose a smoking-free law."

The Lightwood study appears in the early online issue of Circulation: Journal of the American Heart Association. The Meyers study and the Schroeder editorial appear in the Sept. 29 issue of the Journal of the American College of Cardiology.