People who exercised for about half an hour a day tended to have a lower risk of stroke, according to a cohort study adding evidence that physical activity is protective for cardiovascular health.
Based on accelerometer measurements, the most sedentary subjects in the REGARDS study cohort had a 44% increased risk of stroke approaching statistical significance (HR 1.44 for subjects with the highest tertile versus the lowest tertile per sedentary time, 95% CI 0 .99-2.07), Steven Hooker, PhD, dean of San Diego State University’s College of Health and Human Services, California, and colleagues reported.
For each hour of inactivity, the risk of stroke increased linearly (HR 1.14, 95% CI 1.02-1.28). Long periods of sitting were also linked to stroke, according to Hooker’s group article in JAMA network opened†
“Our results add to a growing body of scientific evidence demonstrating the health risks of prolonged sitting,” said study co-author Keith Diaz, PhD, an exercise physiologist at Columbia University in New York City. “We can now add stroke to the growing list of health problems for which prolonged sitting can increase the risk, including cancer, heart disease and early death.”
“If you have a job or lifestyle that requires you to sit most of the day, we recommend taking frequent exercise breaks,” he said. MedPage today† “This one behavior can reduce your risk of stroke.”
Previous studies have linked exercise to a consistently reduced risk of stroke (albeit based on self-reported measures of physical activity, a method subject to recall bias and overestimation of total physical activity). And when strokes do occur, they were… milder in those who exercised regularly†
Hooker’s group reported that it took 25 minutes of objectively measured daily physical activity of moderate to vigorous intensity to see a significant reduction in strokes. This is in line with the current CDC activity guidelinesindicating that adults exercise about 25 minutes per day (150 minutes per week).
However, the study authors suggested that people still have a lower risk of stroke if they exercise for less than 25 minutes. Because of this discrepancy, they wrote that more needs to be done to determine whether the threshold to exercise can be lowered.
For people unable or unwilling to engage in moderate-to-vigorous exercise at recommended levels, the authors found that low-intensity exercise, expressed as a continuous variable, was still associated with less stroke.
Caution is advised, however, as the amount of accumulated daily time spent in [light-intensity physical activity] that was associated with a reduced risk of stroke in this cohort was 4 to 5 hours. This amount is not trivial and is likely to be achieved only with concerted effort,” Hooker and colleagues wrote.
For their study, the authors collected data on more than 7,600 participants in the REgards study.
The study cohort had a mean age of approximately 63 years and 54.5% were female. More than two-thirds were white. About one in three lived in the US stroke belt known for its high death rates from stroke; 21.5% came from the stroke buckle, a region within the stroke belt associated with even higher deaths from stroke.
The researchers followed the participants for about 7.4 years and found 286 cases of stroke during the study period. More than 85% of these were ischemic strokes.
Accelerometer measurements divided individuals into sedentary, light, and intense exercise groups. Hooker and colleagues found that longer periods of exercise in both intensity groups were associated with a lower risk of stroke.
A limitation of the study was that the accelerometer did not measure the types of exercises performed by the participants.
“The accelerometer cannot distinguish between postures (such as sitting versus standing); therefore, we relied on a definition of sedentary behavior on intensity alone. Therefore, sedentary time may be overestimated because some standing may also have been included,” the authors wrote. authors.
The study was funded by a grant from the National Institute of Neurological Disorders and Stroke and the National Institute on Aging.
Hooker reported no conflict of interest.
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