Health

Many strokes can be prevented. If you've had a stroke, you can cut your odds of having another one with medical treatment as well as changes in your diet and other health habits. If you've never had a stroke, you can reduce your risk of ever having one.

Preventing stroke is largely a matter of healthy living and having regular checkups to detect conditions that can lead to stroke, such as hypertension, heart disease, high cholesterol, and diabetes. All adults age 20 and older should have their blood pressure checked every two years if it is normal and at least yearly if it is higher (see "Lower your blood pressure"). They should have their cholesterol checked every five years using a fasting lipid profile, according to the National Heart, Lung, and Blood Institute (see "Lower your cholesterol"). The American Diabetes Association, the Centers for Disease Control and Prevention, and the National Institutes of Health recommend diabetes testing for all healthy Americans 45 and older. People under 45 who are overweight and have one or more other risk factors for diabetes, such as a family history of the disease, should talk to their doctors about having their blood glucose levels tested (see "Control diabetes"). Here are some of the things you can do to lower your risk of stroke:

• Maintain a normal blood pressure (the most important step).
• Maintain a normal cholesterol level.
• Maintain a normal weight.
• Don't smoke.
• Reduce animal fats in your diet, including butter and other dairy fat, and eat at least five servings of fruits and vegetables daily.
• Exercise regularly.

Know the risk factors

You can't control some risk factors, such as age. But you can reduce or eliminate other risk factors through lifestyle changes or medical treatment.

The risk factors you cannot control:

• Age: People over 55 are at higher risk of stroke than are younger people.
• Race: People of African descent have a higher risk of stroke.
• Family medical history: Your risk of stroke is higher if someone in your immediate family has had a stroke.
• Heart disease: Your risk of stroke is higher if you have had a heart attack or if you have certain other heart conditions, such as atrial fibrillation. (However, you may be able to reduce your risk by taking medications and making lifestyle changes to keep blood pressure and cholesterol levels within healthy ranges.)
• Diabetes: Your risk of stroke is higher if you have diabetes. (But you may be able to reduce your risk: See "Control diabetes.")
• Migraine: Having migraine headaches doubles your risk of having a stroke.

Risk factors you can control:

• Hypertension (high blood pressure)
• High cholesterol
• Smoking
• Obesity
• Physical inactivity
• Heavy alcohol consumption
• Diet high in salt and saturated fats
• Use of hormone-based contraceptives and hormone therapy for menopause.

It's important to be aware that as many as half of all strokes cannot be explained by high blood pressure, diabetes, and the other established causes. Therefore, doctors strongly suspect that there are other risk factors not yet identified. Even so, you can take steps to protect yourself, based on the risk factors that are known.

Lower your blood pressure

Untreated hypertension is the leading cause of all types of stroke in the United States, and controlling blood pressure is probably the most powerful weapon in the preventive arsenal. High blood pressure damages vessel walls, and this damage sets in motion a domino effect of problems that can culminate in a stroke. It encourages scarring, which in turn leads to plaque buildup and, eventually, atherosclerosis.

Blood pressure measurements are written as a pair of numbers: The systolic pressure (the top number) is a measure of the pressure the blood exerts against the arterial walls when the heart contracts. Diastolic pressure (the bottom number) is the pressure between contractions. Normal blood pressure is considered to be less than 120/80 mm Hg (see Table 2).

A person with a blood pressure of 160/95 mm Hg is about 4 times more likely to have a stroke than someone with normal blood pressure. Even if just one of the blood pressure numbers is elevated, your risk of stroke rises. In a review of 9 studies that involved 420,000 people, those with the highest diastolic blood pressure (105 mm Hg) were 10 times more likely to have a stroke than those with the lowest (76 mm Hg). Elevated systolic blood pressure also increases the risk of stroke. Many elderly people, especially women, have isolated systolic hypertension, a condition in which only the first of the two blood pressure numbers is elevated.

High blood pressure is often called "the silent killer" because it rarely causes symptoms. The only sure way for you to know if you have hypertension is to have your blood pressure checked regularly.

Hypertension can sometimes be lowered by lifestyle changes alone, such as eating a diet rich in fruits, vegetables, fish, and low-fat dairy products; reducing salt intake; exercising regularly; and losing weight. Diets high in potassium may help reduce stroke risk through an association with lower blood pressure.

Often, to effectively control blood pressure, these modifications need to be combined with blood pressure medications, such as diuretics, ACE inhibitors, angiotensin-receptor blockers, or alpha blockers. Many studies have demonstrated that lowering blood pressure is well worth the trouble. Treating hypertension reduces the incidence of stroke by 35%–40%.

Lower your cholesterol

High levels of low-density lipoproteins (LDL), the "bad" cholesterol, help lay the foundation for atherosclerotic plaque, so it's not surprising that lowering LDL can help prevent atherosclerosis and reduce the risk of stroke. The National Cholesterol Education Program has issued guidelines for total cholesterol levels as well as for LDL, HDL (high-density lipoproteins, the "good" cholesterol), and triglycerides (see Table 3).

The safest and cheapest way to treat high cholesterol is to change your diet, increase physical activity, and, if necessary, lose weight (see "Watch your weight"). A diet with proven benefits for cardiovascular health consists of plenty of fruits and vegetables, as well as fish and other foods that contain "good fats" instead of "bad fats." The good fats help increase HDL, the form of cholesterol that enhances the health of your heart and blood vessels. The good fats are polyunsaturated fats (found in vegetable oils, nuts, and fish) and monounsaturated fats (found in olive and canola oils). The bad fats, which raise LDL, are saturated fats (found in meat and dairy products) and trans fats (found mainly in partially hydrogenated vegetable oils).

In 2002, the Health Professionals Follow-up Study, an ongoing study of thousands of men, found that men who ate fish as little as once a month were 43% less likely to have ischemic strokes than men who ate seafood less frequently. The Nurses' Health Study, an ongoing study of thousands of women, found similar results. Data from two long-term studies, the Framingham Heart Study and the Nurses' Health Study, also suggest that people who eat the most fruits and vegetables are less likely to have strokes than those who eat the least.

However, a low-fat diet does not reduce stroke risk, according to findings from the National Institutes of Health's Women's Health Initiative, an 8-year study of 48,835 women published in the Journal of the American Medical Association in 2006. The incidence of stroke was the same for women ages 50 to 79 whose daily calories consisted of less than 30% fat as it was for women whose daily calories from fat were 35%.

You may be able to reach your target cholesterol and triglyceride levels through lifestyle changes alone. Medication is an option if you are unable to lower your cholesterol and triglycerides to your target levels after three months, if your LDL cholesterol is 190 mg/dL or higher, or if you have one or more risk factors for stroke, including cardiovascular disease, diabetes, and high triglycerides (200 mg/dL or higher) and low HDL cholesterol (less than 40 mg/dL). Several clinical trials have found that statins, a class of lipid-lowering drugs, reduce the risk of stroke in people with cardiovascular disease. But there are other medications for reducing LDL and triglyceride levels and raising HDL. Talk with your doctor about which one is best for you.

Avoid tobacco smoke

The risk of stroke is twice as high for smokers as for nonsmokers. Smoking is an independent risk factor for stroke and it contributes to many of the other risk factors: It raises your blood pressure, reduces the level of beneficial HDL cholesterol, damages the protective lining of the blood vessels, and makes blood more prone to clot. The more you smoke, the greater your risk of stroke. In the Framingham Heart Study, men who smoked more than 40 cigarettes a day were twice as likely to have a stroke as were those who lit up fewer than 10 cigarettes a day. A similar pattern has been found in women. Exposure to other people's tobacco smoke also increases the risk of stroke.

Quitting smoking is one of the cornerstones of stroke prevention. In one British study, people who had smoked fewer than 20 cigarettes daily before quitting lowered their risk to the level of those who had never smoked. Although heavier smokers who quit did not eliminate their excess risk, they did decrease it. Results from both the Framingham Heart and Honolulu Heart studies confirm these findings. Switching from cigarettes to pipes or cigars doesn't reduce your risk at all.

Experts recommend a three-pronged approach to quitting smoking: Wear a nicotine patch or chew nicotine gum to help decrease the urge to smoke, join a support group or seek counseling, and learn techniques that will distract you from the thought of smoking.

Watch your weight

Being overweight or obese increases the risk of stroke. You are considered obese if your body mass index (BMI), a ratio of weight to height, is 30 or over (see Table 4). Being overweight, which means having a BMI of 25–29, also increases your risk of stroke. Excess pounds strain the entire circulatory system and predispose you to other stroke risk factors such as high blood pressure, diabetes, high cholesterol, and obstructive sleep apnea. A doctor can recommend a sensible weight-loss plan that relies on both diet and exercise. A reasonable goal is losing 1 or 2 pounds a week.

Download PDF: What's your body mass index?

Boost physical activity

Physical inactivity appears to raise the risk of stroke, according to several studies. The cardiovascular benefits of exercise include making blood less likely to clot, controlling weight, lowering blood pressure, and increasing levels of protective HDL cholesterol.

Guidelines from the National Academy of Sciences recommend that you aim to get an hour of moderately intense exercise on most days. Moderate exercise includes walking briskly (at 3–4 miles per hour) or golfing while carrying or pulling clubs. People who have had a stroke or TIA who are capable of exercising should get at least 30 minutes of moderately intense physical activity on most days to reduce the risk of another stroke. Always check with your doctor before beginning an exercise program.

Control diabetes

If you have diabetes, your odds of having an ischemic stroke are several times greater than those of people without the disease. Diabetes increases the tendency of the blood to form clots, which can dam up the arteries. High blood sugar, the hallmark of diabetes, promotes the development of peripheral artery disease, which can cause blockages in the arteries leading to the brain.

Keeping your blood pressure and cholesterol in control can reduce your risk. Keeping glucose levels within normal limits can lower the risk of stroke in people with type 1 diabetes. It is unclear whether glucose control also reduces the risk of stroke in people with type 2 diabetes, but it can help prevent damage to the small blood vessels in people with this form of diabetes who have had an ischemic stroke or a TIA.

Control other risk factors

The impact of other risk factors may depend on your lifestyle and medical history.

Moderate your drinking

Alcohol plays a complex role in stroke. Moderate consumption (an average of one to two drinks a day for men and one drink a day for women) may actually lower the risk of ischemic stroke, just as it lowers the risk of heart disease. Researchers from Columbia University's College of Physicians and Surgeons in New York tracked the stroke rate of 677 people age 40 and older for 4 years and found that those who consumed 1 or 2 drinks a day had a 45% lower risk of ischemic stroke than those who drank no alcohol. It didn't seem to matter what kind of alcohol; the results were the same for wine, beer, and spirits. But heavy drinkers fared worse. Those who consumed seven or more drinks a day had nearly three times the risk of ischemic stroke. For hemorrhagic stroke, any amount of drinking appears to increase the risk by two to four times.

The reason moderate drinking may reduce the risk of ischemic stroke is that alcohol inhibits blood clotting and raises protective HDL cholesterol. But heavy drinking can cause heart rhythm disturbances and boost blood pressure, thereby increasing the likelihood of a stroke.

Weigh the risks of hormone therapy

The Women's Health Initiative found an increased risk of stroke among women who took either combined estrogen/progestin hormone therapy or estrogen-only therapy for menopause. The study also found an increased risk of blood clots from hormone therapy.

If you are considering hormone therapy to control menopausal symptoms, discuss the risks and benefits with your doctor. Using this therapy on a short-term basis to relieve troubling symptoms such as hot flashes is generally considered safe. If you have had an ischemic stroke or a TIA, the American Heart Association/American Stroke Association does not recommend hormone therapy.

There is no convincing evidence that most healthy women who use low-dose oral contraceptives have an increased risk of stroke. However, women taking the pill who smoke and have migraines, high blood pressure, or blood-clotting problems have a higher risk, especially if they have a family history of stroke. The contraceptive patch may pose a higher risk of blood clots than oral contraceptives because it delivers 60% more estrogen into the blood. The FDA is studying the issue.

Treat atrial fibrillation

Atrial fibrillation is a common arrhythmia, or heart rhythm disturbance that affects about two million people in the United States. For reasons that aren't fully understood, the upper chambers of the heart (the atria) quiver erratically. As a result, blood swirls around and pools inside the upper chambers, especially the left atrium. The stagnant blood in the left atrium may form clots that can cause a stroke if they break loose and make their way to the brain (see Figure 16).

Figure 16: Atrial fibrillation and stroke

Atrial fibrillation

During atrial fibrillation, the upper chambers of the heart (atria) quiver rapidly rather than contract forcefully. Blood pools along the walls of the left atrium, eventually forming clots that may break free to travel through the left ventricle to the aorta. If the clot lodges in an artery to the brain, it may obstruct blood flow downstream and cause an ischemic stroke.

Experts estimate that atrial fibrillation, which is most common among people over 65, causes more than 75,000 strokes per year, or nearly 10% of all strokes. In the Framingham Heart Study, atrial fibrillation was blamed for 1 of every 4 strokes among people over 80. Taking medications that prevent blood clotting can reduce the risk of stroke by 68% in people with atrial fibrillation in addition to other stroke risk factors.

Prevent or treat other heart conditions

Having a heart attack (myocardial infarction) can cause an embolic stroke. The damaged part of the left ventricle (the lower chamber that pumps blood into the aorta) does not contract normally. Blood tends to pool along the nonfunctional area, permitting small clots to form. A blood clot may form at the site of the heart attack, then break off and, like a ball in a pinball machine, travel to the brain and lodge in a blood vessel there, cutting off the brain's blood supply. About 3%–4% of people who have a heart attack go on to have an embolic stroke, almost all of these occurring in the first month following the heart attack.

Stroke risk is also higher for people with other heart conditions that increase the chance of clot formation, such as congestive heart failure, left ventricular hypertrophy (a thickening of the wall of the left ventricle), valve disease, or arrhythmias. Proper treatment of these conditions can help prevent stroke.

Know your family medical history

As with many other illnesses, the risk of stroke runs in families. Genetic factors influence blood clotting and the development of atherosclerosis and hypertension, all of which affect the risk of stroke. Aneurysms and arteriovenous malformations, two conditions that cause hemorrhagic strokes, clearly have a genetic basis. But genes alone may not be at fault. In addition to sharing many genes, relatives may also share eating habits and other behaviors that can promote strokes. If you have a strong family history of stroke, talk with your doctor about preventive measures you should take.

Control sleep apnea

Obstructive sleep apnea is a life-threatening disorder, most common among overweight men, in which breathing stops hundreds of times each night. It occurs when the upper airway is blocked by excess tissue such as a large uvula, tongue, tonsils, fatty deposits, or a floppy rim at the back of the palate. The hallmark of this condition is heavy snoring, but many snorers do not have this problem.

Because up to 44% of strokes occur during sleep, some researchers believe that obstructive sleep apnea may trigger some TIAs or strokes. Some research has found that people who had these events were much more likely to have a history of sleep apnea than their healthy peers. So far, however, researchers have not yet established how obstructive sleep apnea may cause a stroke.

If apnea can't be reduced by losing weight, avoiding alcohol, and discontinuing medications that may suppress breathing, then ventilation, drugs, or surgery may be necessary.

Detect carotid bruit

Carotid bruit is an abnormal rushing sound made by blood flowing through a narrowed vessel. Doctors may be able to hear it when they press a stethoscope against either one of the carotid arteries, which run up the left and right sides of the neck. Although people who have carotid bruits have an elevated risk of heart disease and stroke, less than half of those with bruits actually have a significant obstruction or narrowing of the carotid artery. Many experts recommend that, after a bruit is detected, physicians perform a more sensitive ultrasound test (see "Doppler ultrasound").

Even if the carotid artery is not severely obstructed and you have not had a TIA or a stroke, you'll still need to take some preventive measures against stroke, such as quitting smoking, losing weight, exercising regularly, and improving your diet. Your doctor may also recommend that you take medication to reduce your blood pressure, cholesterol, or both. Your doctor will probably want to monitor the blockage by scheduling periodic ultrasounds.

If the narrowing increases, or if you develop symptoms, you may need carotid endarterectomy, surgery to remove the obstruction. This surgery is necessary if you have a narrowing that is severe enough to cause blood pressure in the affected artery to drop (see "Carotid endarterectomy"). If you are a candidate for carotid endarterectomy but the surgery is too risky for you, your doctor may prescribe warfarin, an anticoagulant, to help prevent stroke.

How blood clots

The delicate balance between blood flow and blood clotting is maintained by an intricate system whose chief components are platelets and coagulation factors. Platelets are cell-like structures that circulate in the blood. Normally they are shaped like discs and are inactive, but when they receive a chemical signal that says a blood vessel has been injured, they change shape. They also become bristly, like Velcro. These "activated" platelets then stick to the damaged section and to one another. At the same time, coagulation factors circulating in the blood interact with the platelets to create a fine, gel-like mesh. The result is a blood clot.

Drugs known as blood thinners interfere with clot formation in one of two ways. Anticoagulants such as warfarin (Coumadin) inhibit the coagulation process. Antiplatelet agents, such as aspirin or clopidogrel (Plavix), inhibit the action of the platelets. A thrombolytic such as recombinant tissue plasminogen activator, known as tPA (Activase), dissolves blood clots by converting plasminogen (a chemical in the blood) to the enzyme plasmin, which in turn breaks down fibrin, the long, stringy proteins that are the main component of blood clots.

Source: from Harvard Health Publications, Copyright © 2008 Harvard University. All rights reserved. Harvard Medical School does not endorse products.
Used with permission of StayWell.
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