Laughter Keeps Blood Flowing
Through Arteries

by Lee Bowman
Scripps Howard News Service

Laughter may not be the best medicine, but when it comes to healthy, functioning blood vessels, it doesn't hurt. A study shows that a few giggles help expand blood flow.

Researchers at the University of Maryland School of Medicine found that laughter seems to cause the tissue that forms the inner lining of blood vessels to relax or expand, increasing blood flow. Mental stress causes the opposite - making vessel linings constrict and thus reducing blood flow.

That finding confirmed earlier studies suggesting a link between emotional stress and the narrowing of these linings, called the endothelium.

"The endothelium is the first line in the developing of atherosclerosis, or hardening of the arteries," said Dr. Michael Miller, principal investigator for the study, "so, given the results of our study, it is conceivable that laughing may be important to maintain a healthy endothelium and reduce the risk of cardiovascular disease." At the very least, laughter offsets the impact of mental stress, which is harmful to the endothelium."

Miller is director of preventive cardiology at the University of Maryland Medical Center and an associate professor of medicine.

The Study
The study was presented before the American College of Cardiology's scientific meeting in Orlando, Fla. It involved 20 nonsmoking, healthy volunteers, equally divided between men and women, with an average age of 33. All had normal blood pressure, cholesterol and blood glucose levels.

Each participant was randomly assigned to watch parts of two movies at opposite ends of the emotional spectrum - 15-minute clips from a movie like the graphic war depiction, "Saving Private Ryan," or the bowling comedy, "Kingpin". At least 48 hours later the volunteers were showed a movie intended to produce the opposite emotional extreme.

Before each screening, the volunteers fasted overnight and were given an ultrasound to see how well a main blood artery in an arm responded after a blood-pressure cuff was applied and then released.

The same test was done again after each movie, and the researchers noted that the changes in blood-vessel reactivity persisted for at least a half hour to 45 minutes.

There was no great difference in vessel dilation during either the mental stress or laughter phases, but there were sharp contrasts after the movies were seen. Blood flow was reduced in the artery in 14 out of 20 volunteers after seeing the clip that caused mental stress. Beneficial vessel relaxation increased in 19 of the 20 volunteers after they watched laughter-generating segments.

Overall, the average blood flow increased 22 percent in response to laughter, and decreased by 35 percent from mental stress.
Miller said the study was not able to determine exactly how laughing benefits the vessels.

"Does it come from the movement of the diaphragm muscles as you chuckle or guffaw, or does it come from a chemical release triggered by laughter, such as endorphins?" he wondered. On the other hand, nitric oxide is known to play a role in dilating blood-vessel linings, and he said it's possible that stress leads to a breakdown of the compound or impedes production of it, leading to a narrowing of vessels.

But no matter the mechanics, the study is further testament to the benefits of a positive attitude.

"The magnitude of change we saw is similar to the benefit we might see with aerobic activity, but without the aches, pains and muscle tension associated with exercise," Miller said.

"We don't recommend that you laugh and not exercise, but we do recommend that you try to laugh on a regular basis. Thirty minutes of exercise three times a week and 15 minutes of laughter on a daily basis is probably good for the vascular system."

(edited by David Van Alstyne)
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