June 7, 2001 DALLAS, June 1 – For the first time, stress has been linked to increased stroke risk in a population study of middle-aged white men, researchers report in the June issue of Stroke: Journal of the American Heart Association.
“We’ve found that exaggerated blood pressure reactions to stress are related to a greater risk of having a stroke. This is an important area of research to pursue, given the increasing prevalence of stroke in our aging population,” says the study’s lead author Susan A. Everson, Ph.D., an assistant research scientist in the department of epidemiology at the University of Michigan, Ann Arbor.
The study followed 2,303 Finnish middle-aged white men for 11 years who were enrolled in the Kuopio Ischemic Heart Disease (KIHD) risk factor study at the University of Kuopio in Finland. The KIHD study is an on-going study of biological, socioeconomical and psychosocial risk factors that may be involved in heart and blood vessel disease.
To determine the men’s reaction to stress, researchers compared their resting blood pressure (baseline) with readings taken just before an exercise tolerance test on an exercise bicycle a week later.
“It’s not just getting on a bicycle and going for a ride outdoors,” Everson explains. “This is a population of men who know that they are about to undergo an exercise stress test that is used to diagnose heart disease. And they know that they live in a region of the world where there are very high rates of heart disease in men.”
Researchers measured systolic blood pressure, the top number in a reading that represents the pressure while the heart is beating and the diastolic, the bottom number that represents the pressure between heartbeats. They defined systolic blood pressure (SBP) reactivity and diastolic blood pressure (DBP) reactivity as the change in the readings when the men were anticipating the bicycle test compared to their average baseline readings. Elevations in blood pressure during this anticipation phase are considered a measure of cardiovascular activation in response to psychological and behavioral stress, says Everson.
The men who had above-average systolic blood pressure spikes in anticipation of the exercise test had a 72 percent greater risk of any stroke than men with less reactive blood pressures. These men also had an 87 percent greater risk of ischemic stroke – those caused by blood clots rather than bursting of a brain vessel. Each 1-millimeter of mercury increase in systolic pressure in the anticipation phase corresponded to a 1.5 percent increased risk of ischemic stroke. Of the 113 strokes that occurred during the follow-up, 90 were ischemic. There were not enough instances of hemorrhagic stroke to make an association.
In addition, the researchers noted that men with the least amount of education (primary school or less) had an increased risk of stroke compared to those with more schooling. And the two risks were cumulative: men with both high reactivity and poor education had three times the risk of stroke, Everson says.
This study fits into a growing body of epidemiological evidence on mind-body connections in disease development, Everson says. The body’s sympathetic nervous system reacts to mental or emotional stress by increasing blood pressure, heart rate and respiration, for instance. Her research group previously found that a reaction to stress is linked to the development of two known risk factors for heart disease and stroke: high blood pressure and atherosclerosis – the narrowing of the arteries due to a buildup of fat, cholesterol and other substances.
“I think people should recognize that physical changes occur when they are under stress that can have adverse cardiovascular effects,” says Everson. She cautions that it is unknown if women, non-whites or younger people would have the same risk. Still, she says it’s a good idea to heed all the advice available on how to handle stress: such as eating a healthy diet, getting regular exercise and trying to minimize exposure to stressful situations whenever possible.
“Our findings add to the literature that seeks to further our understanding of the critical role that stress plays in the development and progression of atherosclerosis and its clinical complications,” she says. “The more we know about factors that might increase the risk of stroke the greater the likelihood that we can work towards prevention.”
This study was funded in part by the National Heart, Lung and Blood Institute.
Co-authors include: John W. Lynch, Ph.D.; George A. Kaplan, Ph.D.; Timo A. Lakka, M.D., Ph.D.; Juhani Sivenius, M.D., Ph.D.; and Jukka T. Salonen, M.D., Ph.D.
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The above story is reprinted from materials provided by American Heart Association.
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