The old saying that "laughter makes you live longer" is true, especially when it comes to heart health.

A recent study has shown that laughing causes the tissue inside the heart to expand – and increases the flow of oxygen through the body.

Coronary artery disease patients who were involved in a course of laughter therapy had reduced inflammation and had better health, research found.

"Our study found that laughter therapy increased the functional capacity of the cardiovascular system," said lead author Prof. Marco Saffi.

People with heart disease can be invited to comedy nights, or encouraged to enjoy fun evenings with friends and family. People should try to do things that make them laugh at least twice a week."

"Laughter helps the heart because it releases endorphins, which reduce inflammation and help the heart and blood vessels relax," Saffi said. "It also reduces levels of stress hormones, which put a strain on the heart."

The data were presented in Amsterdam at the annual meeting of the European Society of Cardiology, the world's largest heart conference.