Public speaking and similar stress-inducing situations stimulate a physical reaction in two ways: The heart pumps harder and the blood vessels stiffen, leading to a rise in blood pressure. In some people the rise is mainly due to the increase in heart output, while in others it's due to the increased resistance to blood flow in the vessels.
Previous studies have shown that psychological stress acutely affects the immune system and that chronic stress can lead to a diminished capacity to fight off illness.
Cardiac reactors, as the heart-pumping contingent are known, showed changes in measures of immune system activity that were not seen in the vascular reactors, says Noha H. Farag, M.D., of the University of California, San Diego, in research published in the August issue of Brain, Behavior and Immunity.
"These findings suggest that cardiac reactors have a greater immunologic response to stress," the researchers say.
This response was seen in the redistribution of lymphocytes, a type of white blood cell that is a component of the fight-or-flight system and may effect how quickly the immune system can react to new challenges, they say. Such reactions may play a role in inflammatory diseases and heart attack.
The study included 56 healthy men and women who were monitored before and after giving two speeches based on stressful scenarios: being accused of shoplifting and confronting a car dealer who failed to honor a warranty. Blood samples were also taken to assess the immune system measures, such as lymphocyte redistribution.
"Cardiac and vascular reactors can be differentiated on the basis of immunological changes. Interestingly, it is only cardiac responders that show a significant redistribution of lymphocytes in response to stress," Farag says.
The study was funded with grants from the National Institute on Aging and the National Heart, Lung and Blood Institute.
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Brain, Behavior and Immunity: Contact Dr. Robert Ader, editor-in-chief, at (585) 275-5922 or visit www.apnet.com/www/journal/bi.htm.