The researchers defined light activity as walking at normal pace and moderate activity as brisk walking, swimming, and running.
She and her colleagues emphasize, however, that due to the nature of their study, their findings do not prove that physical activity actually reduces stroke severity — only that there is a significant link to it.“While exercise benefits health in many ways,” says study author Katharina S. Sunnerhagen, of the University of Gothenburg in Sweden, “our research suggests that even simply getting in a small amount of physical activity each week may have a big impact later by possibly reducing the severity of a stroke.”
Commenting on the study, Nicole Spartano and Julie Bernhardt, both of Boston University School of Medicine in Massachusetts, say that while the underlying mechanisms are not fully understood, exercise likely helps maintain the brain’s complex system of blood vessels.
A major cause of disability
Stroke is a major cause of significant disability in adults. In the United States, where approximately 795,000 people have a stroke every year, it is the fifth main cause of death.
There are two main kinds of stroke: ischemic, which occurs when a blood clot or constriction in an artery stops blood flow in part of the brain; and hemorrhagic, which happens when a blood vessel ruptures, causing a bleed in the brain.
Both types of stroke stop oxygen and nutrients from reaching brain cells, which eventually — starved of this sustenance — will die.
The amount of disability that can follow a stroke depends on its location and the number of cells killed. It can, for example, result in difficulty walking, talking, and thinking.
Data came from registries and self-reports
The study data came from 925 people — aged 73 years, on average — in Sweden who had had a stroke. Sunnerhagen and colleagues identified them from stroke registries that gave information about the severity of the stroke.
Symptoms such as facial, arm, and eye movement, as well as language ability and consciousness level, determined the level of severity. Based on this, 80 percent of the cohort were classed as having had a “mild” stroke.
The individuals had also answered questions following their stroke about the extent to which they engaged in leisure time physical activity in the period before the stroke. Where necessary, the team confirmed the answers by checking with relatives.
Walking for at least 4 hours each week was classed as light activity, while more intensive exercise, such as swimming, running, and brisk walking for 2–3 hours per week, was classed as moderate activity.
In this context, 52 percent of study participants were inactive in the period leading up to their stroke.
Studies that rely on self-reported physical activity levels often cite this as a possible weakness or limitation of the research. In this case, the researchers are especially cautious about their findings because stroke can affect memory and the questions were put to the individuals after they’d had a stroke.
Exercise, younger age tied to milder strokes
The analysis revealed that those whose physical activity levels were light to moderate in the period leading up to their stroke had double the chance of having a mild stroke compared with those who were inactive.
Of the 59 people whose physical activity levels in the period before their stroke were moderate, 53 (89 percent) had a mild stroke. Of the 384 people whose physical activity level was light, 330 (85 percent) had a mild stroke. Of the 481 who were inactive, 354 (73 percent) had a mild stroke.
When the researchers considered the effect of younger age on stroke severity, however, they saw that physical activity accounted for only 6.8 percent of the differences between the active and inactive groups.
The team suggests that further research should now be done to clarify the extent to which exercise might reduce stroke severity.
Sunnerhagen also advises that “physical inactivity should be monitored as a possible risk factor for severe stroke.”
Spartano notes that animal studies have revealed that physical activity helps safeguard the brain’s complex network of blood vessels by boosting the ability for several arteries to supply the same regions of the brain.
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