“Abrupt changes in body position caused by sudden loud noises, calls for help or other unexpected events occurred within two hours of stroke onset in more than one-fifth of the stroke patients we studied,” says Silvia Koton, M.Occ.H., R.N., of the department of epidemiology and preventive medicine at Tel Aviv University.
Ischemic strokes are the most common type of stroke. They occur when a blood clot blocks blood flow in an artery to the brain.
Researchers assessed the potential stroke-triggering effects of emotional stress, anger, sudden physical effort, sudden changes in environmental temperature and sudden changes in body position. By comparing activities the day of the stroke to the previous day, participants acted as their own control group, making this a prospective case-crossover study.
The relative risk of stroke among patients exposed to at least one trigger during a two-hour “hazard period” preceding the stroke was more than seven times higher compared to similar exposures during the same two-hour period the day before the stroke.
The stimulus with the highest risk was a sudden change in body position or posture. Negative emotional stress/anger was second highest.
Several studies have examined the triggering effect of selected personal and environmental factors on the risk of heart attacks. It has been shown, for example, that heavy physical exertion can trigger a heart attack within less than an hour, probably by dislodging fragments of plaque from the arteries, which then block blood supply to the heart. But until now it hasn’t been clear whether similar factors act as triggers for ischemic stroke.
“The triggering mechanism for ischemic stroke may be comparable, in part, to that for a heart attack, but the mechanisms underlying ischemic stroke are more complex than those underlying heart attack,” says Koton. “Various triggers may act differently and we are studying those issues. Even if the hazard period for stroke turns out to be different than two hours, the information we’re collecting will still allow us to assess the influence of this type of exposure during a given time period.”
Thus far, the Israeli researchers have examined 150 stroke patients – 39 percent women, average age 68. Those with dementia or aphasia (difficulty speaking or understanding words) were excluded. They were interviewed one to four days after having a stroke. Sixty-seven patients (44.7 percent) reported experiencing potential triggering events during the two hours prior to onset of their strokes. Of those, 33 patients (22 percent) reported sudden changes in body position, and 20 (13.3 percent) reported negative emotional stress.
Estimates of the risk associated with other triggers studied will require a larger sample size, say researchers.
“The most important finding of this study is the recognition of new risk factors for ischemic stroke that function as short-term triggers rather than factors such as hypertension and smoking, which affect long-term risk,” says Koton. “Older people, in particular, need to be aware of the potential negative influence of reactions to emotions and to sudden exposure to familiar, but startling activities such as a ring of a doorbell or telephone.”
As a preventive step, the public should be informed of the various potential triggers for stroke.
“Stress and anger-coping programs could be offered to high-risk groups,” she says. “The possibility of prescribing preventive medications to specific high-risk groups also needs to be investigated.”
The study is a joint project of Tel Aviv University’s Sackler Faculty of Medicine, the Israel Center for Disease Control and the Sourasky and Sheba Medical Centers in Tel Aviv. Other researchers taking part in the study include Natan M. Bornstein, M.D.; David Tanne, M.D.; and Manfred S. Green, M.D., Ph.D.