Stroke Can be Prevented

Summarized by Robert W. Griffith, MD
January 24, 2003 (Reviewed: January 21, 2005)

Introduction

Stroke is the third leading cause of death in developed countries, and trying to prevent it deserves our attention. We have already posted several articles on these pages about ways in which one can try to avoid a stroke. Many of these measures have been found to be effective in clinical trials. Now a Canadian group of physicians have analyzed the medical literature to find out just how valuable some treatments can be.

The numbers quoted here are only those where the evidence is strong, i.e. obtained from well-controlled clinical trials or observations on large numbers of people.

Known risk factors

The known risk factors for stroke are given in the table:

Risk Factor	Relative Risk (RR)
High blood pressure	3 to 5
Physical inactivity	2.7
Raised cholesterol level	1.8 to 2.6
Obesity	1.8 to 2.4
Carotid artery narrowing	2
Alcohol: over 5 drinks a day	1.6
Smoking	1.5

By 'relative risk', or RR, one means the number of times stroke is likely to occur in persons with the risk factor, compared with those without that risk factor.

There are some risk factors you can't do anything about - increasing age, being male, being African American, Hispanic or Asian, having a family history of stroke, having coronary heart disease, or congestive heart failure.

Two conditions in particular carry a higher risk of stroke. Transient ischemic attacks (TIAs) are often called 'mini-strokes', and carry an 11% risk of the person having a stroke, often within 2 days of a TIA. And atrial fibrillation, a type of irregular heartbeat, is associated with a RR of stroke of 5 to 17.

Preventive steps

Stroke risk factors have been known for decades (even if their RRs of stroke were not known), but the benefits of tackling each one have only quite recently been calculated:

1. Lowering blood pressure in people where it's necessary reduces the RR of stroke by over 40%. In elderly persons with 'isolated systolic hypertension' - just the first number is increased - treatment reduces the RR by 30%. The greater the reduction in blood pressure, the greater the risk reduction. All classes of blood pressure drugs are effective in this respect.
2. Statin drug treatment for high cholesterol levels is associated with a RR reduction of 25%. Other lipid-lowering therapies, such as diet or fibrate drugs, aren't effective in reducing the stroke risk.
3. Patients with untreated atrial fibrillation have a risk of stroke of about 5% every year. This is because the irregular heartbeat allows small clots to develop in the upper chambers of the heart, one of which may break off and travel in the blood stream to block a brain artery. However, the anticoagulant drug warfarin is highly effective in preventing stroke; and it's major side effect, bleeding, can be eliminated by correct blood testing and dosing.
4. Patients who have had a heart attack (a myocardial infarction or MI) have an increased risk of having a stroke. This RR can be cut by 36% by the use of small doses of aspirin. However, aspirin hasn't been shown to help in reducing stroke in 'normal' people.
5. Stopping smoking reduces the RR of another stroke by 33% in people who have already had a stroke, although it doesn't seem to be helpful in preventing a first stroke, at least in clinical studies.
6. People with partially blocked carotid arteries (due to atherosclerosis) have a 30% reduction in their RR of a stroke over a 3-year period if they undergo surgical removal of the tissue causing the blockage; however, there is a fairly high risk of death from postoperative complications in the first few days after this surgery. Obviously, we need to learn which patients will benefit most from this operation.

Around 7% of all patients with a stroke or TIA will have a repeat event each year. It's clear, therefore, that preventive steps like those listed above are much more important in patients who have already had a stroke or a 'warning' in the form of a TIA.

Comment

Although the published analysis didn't include all the lifestyle changes usually considered to be 'heart healthy' - appropriate diet, weight control, physical exercise, no smoking, etc. - it's well known that adapting them would have a beneficial effect on the risk of stroke. Indeed, we have posted several articles that show this (see the links below).

Anyone with high blood pressure, high cholesterol, or other risk factors, should visit their physicians to ensure that they are receiving the appropriate treatment to prevent the likelihood of their having a stroke.

Source

• New evidence for stroke prevention. SE. Straus, SR. Majumdar, FA. McAlister, JAMA, 2002, vol. 288, pp. 1388--1395

Related Links
Fitness Helps Men Avoid Stroke
Fish Appears to Reduce Stroke Risk in Women
Can Vitamin E Help Women Avoid Stroke?

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