MedWire News: A bout of vigorous exercise may cause a temporary increase in stroke risk, particularly among people who do not habitually exercise, research shows.
People's risk for stroke more than doubled during the hour following a bout of moderate or vigorous exercise, report Murray Mittleman (Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA) and colleagues.
However, the risk increase was considerably smaller among people who usually exercised at least three times per week than among habitually sedentary people.
The findings emerge from the Stroke Onset Study, for which the team interviewed 390 patients with ischemic stroke about their activities preceding symptom onset. The study uses a case-crossover design to identify stroke triggers, such as occasional coffee intake, which the team has previously suggested as a trigger.
In all, 21 (5%) of the patients engaged in moderate or vigorous activity in the hour before stroke onset, while six patients lifted an object weighing at least 50 pounds (23 kg).
Such activities have acute effects - including an increase in heart rate and blood pressure -that could precipitate vascular events, note the researchers.
They report that the risk for ischemic stroke was increased 2.3-fold within the hour after moderate or vigorous physical activity and 2.6-fold after heavy lifting.
Even patients who habitually exercised at least three times a week had a 2.0-fold rise in stroke risk during the hour after a bout of exercise, but this risk increase was markedly higher, at 6.8-fold, among more sedentary patients.
"This study reinforces the importance of habitual physical activity in stroke prevention," say Mittleman et al in the American Journal of Epidemiology.
"Not only does habitual physical activity lower the baseline risk of stroke, it also appears to lower the risk of having an ischemic stroke triggered by an episode of physical activity."
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