Stress linked to increased stroke risk

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 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 says the study's lead author Susan A. Everson, scientist in 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.

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.

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 behavioural stress, says Everson.

The men who had above-average systolic blood pressure spikes in anticipation of the exercise test had a 72 per cent greater risk of any stroke than men with less reactive blood pressures. These men also had an 87 per cent 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.

The 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.

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