Smoking leads to heart failure by causing thickened heart walls and reducing the heart's ability to pump, a new study shows.

The research also found that smoking more and longer over a lifetime were associated with greater heart damage.

Researchers assessed the hearts of 4,580 U.S. adults using echocardiography -- ultrasound of the heart. The participants' average age was nearly 76. None had any obvious signs of heart disease.

Even after accounting for factors such as age, race, body fat, blood pressure, diabetes and alcohol consumption, current smokers had thicker heart walls and reduced pumping function than nonsmokers and former smokers, the study showed.

The study was published Sept. 13 in the journal Circulation: Cardiovascular Imaging.

It's long been known that smoking is linked with heart failure, even in people without heart disease. But, health experts didn't know how smoking increased the risk of heart failure.

"These data suggest that smoking can independently lead to thickening of the heart and worsening of heart function, which may lead to a higher risk for heart failure, even in people who don't have heart attacks," said study author Dr. Wilson Nadruz Jr. He is a research fellow at Brigham and Women's Hospital in Boston.

These findings reinforce the recommendations stating that smoking is dangerous and should be stopped, Nadruz said in a journal news release.

Study senior author Dr. Scott Solomon is a professor of medicine at Harvard Medical School and Brigham and Women's Hospital. "The good news is that former smokers had similar heart structure and function compared with never-smokers," he said.

"This suggests that the potential effects of tobacco on the [heart wall] might be reversible after smoking cessation," Solomon added.