Dr. Virginia Howard, professor in the department of epidemiology at the University of Alabama at Birmingham — in collaboration with Dr. Michelle N. McDonnell, from the University of South Adelaide — was recently invited to give a topical review in the American Heart Association’s journal Stroke to summarize the terminology and measurement of physical activity (PA), describe how PA can ameliorate the effects of stroke risk factors, and synthesize the results of studies of PA and stroke risk in men and women.
Drs. Howard and McDonnell explained that PA is a complex behavior that can incorporate different elements, including occupational or leisure time PA, commuting, sport, walking, and exercise training. The accepted definition of PA used by most researchers is “any bodily movement produced by skeletal muscles that results in energy expenditure.” (This differs from exercise, a subset of PA defined as “PA that is planned, structured, repetitive and purposeful in the sense that improvement or maintenance of one or more components of physical fitness is an objective.”)
It is estimated that 610,000 first strokes occur in the United States each year; worldwide, it is estimated that there were 11.6 million incident ischemic strokes and 5.3 million incident hemorrhagic strokes in 2010. Although transient ischemic attacks can precede stroke, most strokes occur without warning. Stroke is a preventable disease, and control of modifiable risk factors plays the major role in prevention strategies. There is substantial, consistent evidence from numerous, high-quality studies that higher PA levels are associated with significantly lower risk of stroke, suggesting that PA has a protective benefit in stroke prevention beyond the traditional stroke risk factors. With the low prevalence of regular physical activity in the general population, increasing PA levels could, therefore, have a significant effect on reducing stroke incidence. When measuring the impact of PA on stroke risk, it is difficult to separate the specific role of PA because it often clusters with other healthy lifestyle factors, such as healthy diet, not smoking, and maintaining a healthy weight. PA is believed to reduce stroke risk through the positive effect it has on risk factors such as hypertension, diabetes mellitus, and body fat.
Recommendations for future research include conducting cohort studies that include stroke outcomes and objective measurement of PA to supplement self-reported measures to enable more accurate classification of PA levels and assist in clarifying the effect of intensity versus duration and dose-response relationship for men and women.
“Physical Activity in Primary Stroke Prevention: Just Do It!” was published in April.