The researchers measured brachial artery flow, in the forearm, using a blood pressure cuff, before and after each "stimulus."
"In the minute after you release [the rubber bulb], you see how the inner lining of the blood vessel reacts, the endothelial response," Miller said. "People with risk factors for heart disease like smoking and hypertension don't dilate normally. We believe that means that their vasculature is not healthy."
Among the study participants, brachial artery flow increased 26 percent during the joyful music phase and decreased 6 percent after listening to anxiety-producing music.
Blood flow also increased 19 percent during the laughter (video clip) phase and 11 percent during relaxation.
The increase in dilation seen after listening to joyful music was "about the same level we see after someone does aerobic activity. It's also similar to what we see after taking statin medication," Miller said. "The effect lasts for about an hour."
The positive effect may come from the release of endorphins, Miller speculated, referring to the body chemicals that block pain and ease anxiety and depression.
"Clearly, the role of psychological risk factors, and particularly psychological stress, has been neglected in preventive cardiology," Lavie said. "Clearly, extreme emotional stress -- the classic example is public speaking, especially for novice speakers -- has the exact opposite effects as what Miller showed with laughter and relaxing music. Acute and chronic job stress also has deleterious effects which could be countered by laughter or relaxing music."
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