In the largest study to date on the health effects of napping, researchers tracked 23,681 healthy Greek adults for an average of about six years. Those who napped for about half an hour at least three times weekly had a 37 percent lower risk of dying from heart attacks or other heart problems than those who did not nap.

Most participants were in their 50s, and the strongest evidence was in working men, according to the study, which appears in Monday's issue of Archives of Internal Medicine.

The researchers said naps might benefit the heart by reducing stress, and jobs are a common source of stress.

It's likely that women reap similar benefits from napping, but not enough of them died during the study to be sure, said Dr. Dimitrios Trichopoulos, the study's senior author and a researcher at Harvard University and the University of Athens Medical School.

Heart problems killed 48 women who were studied, six of them working women, compared with 85 men, including 28 working men.

A daytime siesta has long been part of many cultures, especially those in warmer climates. Mediterranean-style eating habits featuring fruits, vegetables, beans and olive oil have been credited with contributing to relatively low rates of heart disease in those countries, but the researchers wanted to see if napping also plays a role.

"My advice is if you can (nap), do it. If you have a sofa in your office, if you can relax, do it," Trichopoulos said.

Exactly how stress is related to heart disease is uncertain. Some researchers think it might be directly involved, through unhealthy effects of stress hormones, or indirectly by causing people to exercise less, overeat or smoke.

The researchers in the latest study factored in diet, exercise, smoking and other habits that affect the heart but still found napping seemed to help.

Previous studies have had conflicting results. Some suggested napping might increase risk of death, but those mostly involved elderly people whose daytime sleepiness reflected poor health, Trichopoulos said.

His research team studied a broader range of people, ages 20 to 86, who were generally healthy when the study began.

Still, it's possible that study participants who napped "are just people who take better care of themselves," which could also benefit the heart, said Dr. Marvin Wooten, a sleep specialist at Columbia St. Mary's Hospital in Milwaukee.

"The guy ... who doesn't take time out for a siesta in their culture is probably the guy who is extremely driven and under a lot of pressure," which could increase heart risks, he said.

Siestas aren't ingrained in U.S. culture, and napping usually is equated with laziness in the high-charging corporate world, said Bill Anthony, a Boston University psychologist and co-author of "The Art of Napping at Work."

Still, some offices allow on-the-job naps, and many workers say it makes them more, not less, productive.

Yarde Metals, a metals distributing firm, built a nap room at its Southington, Conn., headquarters as part of an employee wellness program. With two leather sofas, fluffy pillows, soft lighting and an alarm clock, it's the perfect place for a quick snooze, engineer Mark Ekenbarger said.

Ekenbarger, 56, has an enlarged heart artery and said he frequently takes half-hour naps on the advice of his doctor to reduce stress.

"It really does energize me for the rest of the day," Ekenbarger said.

"It would be really encouraging if employers across the country really embraced that philosophy that napping is a good thing. It makes a big difference in my life."