Published online before print September 25, 2003, doi: 10.1161/01.STR.0000095164.20889.72
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(Stroke. 2003;34:2481.)
© 2003 American Heart Association, Inc.
Original Contributions |
Editorial Commen: Physical Exercise and Stroke: The Sitting Majority Has a Lesson to Learn
Department of Neurology and Neurosciences Center, Donauklinikum and Danube University, Maria Gugging, Austria
One of the most simple, natural, and cheapest ways of preventing a stroke is to exercise regularly. In spite of this trivial wisdom it is hard to get people to increase their cardiovascular fitness, probably because no direct gains are visible and no immediate rewards are attached. One report from Canada estimates that about two thirds of the population are inactive, and the public health burden resulting from this amounts to 2.5% of total direct health costs.1 For this sitting majority there is now a lesson to be learned. Lee et al report in this issue of Stroke2 a meta-analysis of all studies published up to mid-2002, including epidemiological as well as case-control studies, showing a clear benefit of physical activity to prevent both stroke incidence and mortality. The magnitude of the effect is considerable, homogenous, and significant: highly active individuals had a 21% lower risk of ischemic stroke and a 34% lower risk of hemorrhagic stroke when compared with low-active individuals.
What has also become evident is that no large differences exist between countries. The studies for this meta-analysis have come from North America and include data from the Framingham cohort and the Northern Manhattan Stroke Study. Other data are from the United Kingdom, Scandinavia, Netherlands, Japan, and Australia. The pooled results show unequivocally that high-level physical activity should become a global recommendation for stroke prevention. Not considering malnutrition and social impoverishment as contributing causes of stroke in less developed countries, there is no reason to assume that physical exercise should be less effective in any other social, cultural, or ethnic setting.
Physical activity has also been shown to reduce cardiovascular diseases as well as stroke in women. Although the authors have not presented a separate analysis for this, the obtainable benefits are also impressive.3,4
Finally, this article also compiles the evidence for a dose-response relationship: High level activity is better than moderate-level activity, but moderate activity is also effective when compared with low-level activity. When all studies are combined, the moderately active individuals had a 20% lower risk of stroke and death than did low-active persons.
This graded effect of reducing the risk of stroke with vigorous levels compared with moderate levels of physical exercise implies more than just a causal relationship. It shows that the moderate approach also is effective in a measurable, significant, and recommendable way. It shows that people inclined to exercise on moderate levels can also expect some advantage to prevent a stroke. But the role of walking compared with vigorous exercise has to be studied further for stroke prevention and has up to now has been only prospectively assessed for the prevention of cardiovascular events.5 This is an important issue for future studies because the moderate activity approach seems to fit best for a mass approach.
A lot of the effects could be due to concomitant risk factor modification such as blood pressure lowering. Wisely, the authors argue that if the effect is via blood pressure reduction, the meta-analysis should not control for it. Still, this has been done in one third of the studies. But the major limitation of this study is that no clear working definitions for intensity of physical exercise have been provided. Most studies use physical activity questionnaires, which are known to be imprecise and biased, especially if quantification is based on self-reported estimates. Other studies have used prespecified categories for light-moderate (such as walking) and heavy physical activity (such as jogging).6 Usually no parallel caloric measurements or weight controls are performed, and no single laboratory marker has been shown practical for concomitant study, even if lipid profiles7,8 and other atherogenic markers such as leukocyte count9 or tumor necrosis factor10could be valuable parameters to monitor risk. On the other hand, surrogate markers such as carotid intima-media thickness cannot be measurably influenced by physical activity.11 Others still recommend peak oxygen uptake or peak energy expenditure as a relation to oxygen uptake when a person is at rest as a robust measure of physical fitness.12
It is now established beyond reasonable doubt that high-level physical activity is to be strongly recommended for the prevention of stroke. Primary care physicians and stroke specialists will now be able to recommend this very effective measure with a higher level of certainty. Still, a truly randomized controlled trial assessing the prospective rates of stroke incidence (or recurrence) is needed. Only such a trial would quantify the true measures of physical activity to be recommended for stroke prevention.
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- Katzmarzyk PT, Gledhill N, Shephard RJ. The economic burden of physical inactivity in Canada. CMAJ. 2000; 163: 1435–1440.
[Abstract/Free Full Text] - Lee CD, Folsom AR, Blair SN. Physical activity and stroke risk: a meta-analysis. Stroke. 2003; 34: 2475–2482.
[Abstract/Free Full Text] - Yu BF, Stampfer MJ, Colditz GA, et al. Physical activity and risk of stroke in women. JAMA. 2000; 283: 2961–2967.
[Abstract/Free Full Text] - Ellekjaer H, Holen J, Ellekjaer E, Vatten L. Physical activity and stroke mortality in women. Stroke. 2000; 31: 14.
[Abstract/Free Full Text] - Manson JE, Greenland P, LaCroix AZ, et al. Walking compared with vigorous exercise for the prevention of cardiovascular events in women. N Engl J Med. 2002; 347: 716–725.
[Abstract/Free Full Text] - Sacco RL, Gan R, Boden-Albala B, et al. Leisure-time physical activity and ischemic stroke risk. Stroke. 1998; 29: 380–387.
[Abstract/Free Full Text] - Sacco RL, Benson RT, Kargman DE, et al. High-density lipoprotein cholesterol and ischemic stroke in the elderly. JAMA. 2001; 285: 2729–2735.
[Abstract/Free Full Text] - Kraus WE, Houmard JA, Duscha BD, et al. Effects of the amount and intensity of exercise on plasma lipoproteins. N Engl J Med. 2002; 347: 1483–1492.
[Abstract/Free Full Text] - Elkind MS, Sciacca R, Boden-Albala B, et al. Leukocyte count is associated with aortic plaque thickness. Stroke. 2002; 33: 2587–2592.
[Abstract/Free Full Text] - Elkind MS, Cheng J, Boden-Albala B, et al. Tumor necrosis factor receptor levels are associated with carotid atherosclerosis. Stroke. 2002; 33: 31–37.
[Abstract/Free Full Text] - Tanaka H, Seals DR, Monahan KD, et al. Regular aerobic exercise and the age-related increase in carotid artery intima-media thickness in healthy men. J Appl Physiol. 2002; 92: 1458–1464.
[Abstract/Free Full Text] - Barady GL. Survival of the fittest: more evidence. N Engl J Med. 2002; 346: 852–854.Editorial.
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