Can a laugh every day keep the heart attack away? Maybe so.

Laughter, along with an active sense of humor, may help protect you against a heart attack, according to a study by cardiologists at the University of Maryland Medical Center in Baltimore. The study, which is the first to indicate that laughter may help prevent heart disease, found that people with heart disease were 40 percent less likely to laugh in a variety of situations compared to people of the same age without heart disease.

"The old saying that 'laughter is the best medicine,' definitely appears to be true when it comes to protecting your heart," says Michael Miller, M.D., director of the Center for Preventive Cardiology at the University of Maryland Medical Center and associate professor of medicine at the University of Maryland School of Medicine. "We don't know yet why laughing protects the heart, but we know that mental stress is associated with impairment of the endothelium, the protective barrier lining our blood vessels. This can cause a series of inflammatory reactions that lead to fat and cholesterol build-up in the coronary arteries and ultimately to a heart attack."