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Causes and Prevention

Strokes have a variety of causes, some which can be avoided through careful attention to lifestyle choices, and some which are not controllable and, if present, must simply be accepted. In general, the more risk factors a person has, the greater their chances of suffering a stroke. However, risk factors only raise a person's risk for having a stroke, they do not make a stroke inevitable. It is possible to have multiple risk factors and never experience a stroke, or vice versa, a person can suffer a stroke without having obvious risk factors.

Here is a list of some of the risk factors for stroke over which people have little control:

  • Age. A stroke can occur at any age. However, risk of stroke increases as people grow older.

  • Family History. Some stroke risk factors run in families and are genetically inheritable. Your risk for stroke is greater than average if you have a close blood relative who has previously had a stroke.

  • Race. Some stroke risk factors are genetically inheritable based on race. For example, African Americans are, on average, at a higher risk for high blood pressure, diabetes and sickle cell anemia than are Caucasians. The same genetic tendencies at work causing higher incidences of high blood pressure, diabetes and sickle cell anemia among African Americans also causes African Americans to have a higher incidence of stroke.

  • Gender. Men are slightly more likely than women to get a stroke. However, women are slightly more likely to die of stroke than men. Women who are pregnant or who are taking birth control pills are at a higher risk for stroke than women who are not.

  • Previous History of Stroke or Heart Attack. If you have had a previous stroke (or a heart attack for that matter), you are at an increased chance of having a stroke.

  • Transient Ischemic Attack. A person who has experienced a transient ischemic attack (TIA) is more likely to have a stroke than an individual who has not. A TIA is sometimes referred to as a 'mini' or 'warning' stroke. TIAs are a temporary type of ischemic stroke caused by a blockage that obstructs blood flow through an artery that feeds the brain. During a TIA, the artery is only blocked for a minute or so and no permanent damage is done. Symptoms of a TIA, by definition, last less than 24 hours. TIAs produce the same short-term symptoms as strokes but do not cause long-term damage.

  • Sickle Cell Anemia. Sickle cell anemia is a genetic disorder that affects the shape of oxygen-carrying red blood cells. The round shape of normal red blood cells helps them to easily carry oxygen. Malformed sickle-shaped red blood cells carry oxygen with less efficiency, and also have a greater tendency to attach to arterial walls forming blockages. Sickle cell anemia most commonly affects African Americans.

Fortunately, there are also many risk factors for stroke that people can control or manage through careful lifestyle choices and appropriate use of medicine:

  • Hypertension. Commonly known as high blood pressure, hypertension is the single largest contributing risk factor to stroke. By some estimates, up to one third of the adult population in the United States has high blood pressure. A far smaller percentage of the population actually receives treatment. Unmanaged hypertension raises a person's stroke risk by four to six times that of people with normal or controlled blood pressure.

    While doctors can prescribe some medicines to help alleviate high blood pressure, the simplest way to combat the condition is to eat a balanced and healthy diet, to maintain proper weight and to exercise daily. Persons at risk for stroke should have their blood pressure checked regularly and comply with their doctor's recommendations for medicine, diet and exercise.

  • Heart Disease. While any form of heart disease increases risk of stroke, the type of heart disease most commonly associated with increased stroke risk is atrial fibrillation. An estimated 15% of strokes are found in people with this heart arrhythmia. In this condition, two of the four heart chambers contract incompletely and at an irregular, fast pace causing erratic blood flow patterns which often result in blood clots. Once formed, clots can travel to the brain causing ischemic stroke by obstructing a cerebral artery.

  • Atrial fibrillation is a treatable medical condition, and persons who suffer from it should seek the care of a physician specialized in cardiology. Refer to our Heart Disease topic center for comprehensive information on the prevention of heart disease.

  • Diabetes. Diabetes, a disease of unregulated blood sugar control, raises people's stroke risk by up to three times normal. It is associated with hypertension and obesity which further increase stroke risk.

    All forms of diabetes can be medically managed. However, some forms of diabetes are responsive to healthy lifestyle choices and can sometimes improve as people take better care of themselves. Refer to our diabetes topic center for comprehensive information on the prevention of diabetes.

  • High Cholesterol. Cholesterol is a naturally occurring fatty material crucial for production and maintenance of the body's cell membranes and hormones. It is manufactured by the body (in the liver), and also is derived from animal food sources, notably eggs, meat and dairy products. People who are genetically built to be efficient producers of cholesterol, or who consume animal foods in excess such that their blood cholesterol is too high are at an increased chance for stroke, because of how excessive cholesterol reacts with the cardiovascular system. Cholesterol and blood are 'immiscible', meaning they cannot mix together (like oil and water). Excess cholesterol in the blood stream tends to clump together and attach to artery walls, forming plaques, in a disease process known as arteriosclerosis. Over time, arteriosclerotic plaques can all but completely block blood vessels feeding the brain. Bits of fatty plaque material (or clotted blood cells) can then break off and lodge in an artery feeding the brain, causing stroke. High cholesterol also can lead to high blood pressure (hypertension) which also increases stroke risk.

  • Tobacco Use. Smoking doubles a person's risk for stroke. Chemicals within tobacco smoke damage arterial walls. These damaged vessel walls provide irregular surfaces where blood clots that can lead to strokes are more likely to form. Smoking also reduces the amount of oxygen present in the blood, making the heart work harder to supply a constant supply of oxygen to the body. It causes other serious and life-threatening diseases including lung and heart diseases.

  • Alcohol Intake. People who drink alcohol excessively (more than one drink a day for women or more than two drinks a day for men) are at increased risk for stroke. Alcohol is associated with heightened blood pressure which, in turn, raises stroke risk.

  • Obesity. Recent research suggests that mid-life obesity (BMI of 30 or greater) is associated with heightened stroke risk for men in future decades even when other risk factors such as stress, smoking, exercise, diabetes or high blood pressure are removed from consideration. BMI stands for Body Mass Index and is calculated as follows: weight in pounds/height in inches x height in inches x 703. There are also internet sites that calculate your BMI, simply type “BMI” into your favorite search engine to find these sites.

  • Sedentary Lifestyle. Physical inactivity directly contributes to many of the risk factors associated with stroke, including obesity, diabetes, and high cholesterol. Getting regular cardiovascular exercise is one of the best ways that you can reduce your stroke risk. Cardiovascular exercises get the heart pumping for sustained periods of time. Examples of cardiovascular exercise include swimming, jogging, brisk walking, and court sports like tennis and basketball. Exercise targets and reduces many of the controllable risk factors for stroke and generally leaves people feeling healthier, less stressed, and more energetic. You should consult your doctor before beginning any exercise plan, as he or she will be in the best position to know what level of activity will be safe for you to engage in.

    In January 2005 the US Department of Health and Human Services revised their recommendations for exercise. Key recommendations include:

    • To reduce the risk of chronic disease you need to engage in 30 minutes of moderate intensity physical activity a day above your usual activity (an example of moderate intensity activity is brisk walking).
    • To help manage body weight and prevent gradual weight gain in adulthood you need to engage in 60 minutes of moderate to vigorous intensity activity on most days of the week.
    • To sustain weight loss you need to engage in 60 to 90 minutes of daily moderate intensity physical activity.

    For more information on these and other recommendations visit the Department of Health and Human Services website at: