The most important thing to know about stroke is how to prevent it. Stroke is a leading cause of death and disability throughout the world. In the United States more than 700,000 strokes each year give rise to staggering financial and emotional burdens. This unfortunate situation is made more regrettable by the fact that many, perhaps most, strokes are preventable.

Many things contribute to the occurrence of stroke, and avoiding a stroke is largely a matter of identifying and reducing risk factors. Some risk factors such as age, gender and race, are not amenable to modification—but many other risk factors are modifiable. Some of these have been known for several decades, while others have been recognized only recently.

Long-recognized risks include high blood pressure, heart disease (especially heart attack and heart arrhythmia, such as atrial fibrillation), diabetes, cholesterol, carotid artery disease, and smoking. By some estimates nearly half of all strokes could be prevented if we would just do three things:

1  Control all cases of high blood pressure

2  Convince all smokers to stop

3  Use appropriate treatment in all patients with atrial fibrillation

Additionally, there is good evidence that treatment of high cholesterol and carotid artery disease can further reduce the risk of stroke.

While the classical risk factors noted above account for the majority of strokes, a substantial minority of patients—perhaps one-third—have none of these classical risks. In recent years, we have discovered additional risks, many of them modifiable. These are briefly summarized below.

Lack of physical exercise increases stroke risk, while regular physical exercise, something as simple as walking for 20 minutes, three times a week, can reduce the risk of stroke and the risk of premature death or heart disease.

Diet influences stroke risk. Higher intake of sodium is associated with increased risk. Replacing saturated fats with unsaturated fats reduces risk. Fruits and vegetables may be protective because of anti-oxidant mechanisms or elevation of potassium levels. Vitamins C and E, along with beta-carotene, are associated with stroke risk reduction. Inadequate intake of vitamin B-12, pyridoxine, and folic acid may contribute to stroke risk by raising homocysteine levels. Heavy alcohol use (more than 4 drinks a day) is a stroke risk factor. Moderate alcohol use (1-2 drinks a day) seems to be protective.

Among the more surprising stroke risks are various infections, especially those involving chlamydia, cytomegalovirus and periodontal disease. And we are learning that many genetic factors influence stroke risk.

The explosion of information about stroke risk offers many opportunities for intervention and prevention, but stroke risk assessment is a complex matter. We are proud that we at the Colorado Neurological Institute, in collaboration with colleagues on National Stroke Association's Stroke Prevention Advisory Board, have recently created a computer-based tool for quantitative measurement of stroke risk. We anticipate that this tool, the Stroke Risk Disk, will improve the awareness of stroke risk factors and the accuracy of stroke prediction. In so doing, we hope that it will also lessen the impact of stroke for everyone.