Stroke Causes and Prevention
Your risk of stroke is influenced by many factors. Some factors, like age, cannot be changed. However, other factors (like high blood pressure) can be minimized by healthy lifestyle choices and medication (if necessary). In general, people with more risk factors have a greater chance 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 conversely, 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, the risk of stroke increases as people grow older.
- Family History. Your risk for stroke is greater than average if you have a close blood relative who has had a stroke.
- Race. The risk of stroke is higher in African Americans (approximately 4%), but lower in Asian Americans (approximately 1.8%) when compared to the rate of stroke throughout the United States (about 2.6%). The higher risk in African Americans may be related to this group's greater risk of having high blood pressure, which greatly increases a person's chance of stroke.
- Gender. Men are slightly more likely than women to experience a stroke. However, women are slightly more likely to die of stroke than men.
- Previous History of Stroke or Heart Attack. If you have had a previous stroke you more likely to have another. Similarly, individuals who have had heart attacks (Myocardial Infarction or MI's) also have a higher risk of stroke. This risk is greatest within the first month following a heart attack and decreases with time. For more information on Heart Attacks, please read our article by clicking here.
- Transient Ischemic Attack. A person who has experienced a TIA (described above, click here to return to that description) is more likely to have a stroke than an individual who has not had a TIA. The risk of having a stroke following a TIA is greatest within the first thirty days, but may persist for as long as three months. Because of the subsequent increased risk of having a stroke, individuals who have a TIA should seek medical treatment as soon as possible.
- Hypercoaguable State: Genetically, some individuals tend to make blood clots more easily than other people, a condition referred to as being "hypercoaguable". As described in the section on Ischemic stroke, these blood clots can clog someone's arteries, or break off and completely block their cerebral arteries, depriving associated brain areas of needed oxygen and nutrients. Hypercoaguable people are at a higher risk of having a stroke.
Fortunately, there are also many risk factors for stroke that people can control or manage through careful lifestyle choices and the appropriate use of medicine:
Hypertension. Commonly known as high blood pressure, hypertension is a major risk factor for stroke. Up to 1/3 of the adults in the United States have high blood pressure. Without treatment, a hypertensive person's stroke risk can be four to six times that of people with normal or controlled blood pressure.Your blood pressure is reported in two numbers (e.g., 130/80). The top number is a measure of the blood pressure when the heart is contracting (i.e., systolic blood pressure). The bottom number, the diastolic blood pressure, is a reading of the pressure in the arteries as the muscle of the heart relaxes after it contracts. It is important that both of these numbers are controlled in order to prevent a first stroke, as well as to decrease the chance of having a second stroke in someone who had a previous event.
In general, to decrease your chance of having a first stroke, your blood pressure should be lower than 140/90. However, if you are diabetic, your blood pressure should be less than 130/80. Depending on your other risk factors, your blood pressure goal may be different.
Initial treatment to control blood pressure includes exercise, weight loss, and a diet low in sodium and high in fruits and vegetables. If lifestyle changes are not sufficient, there are multiple medications available to control your blood pressure and decrease the risk of stroke.
- Atrial Fibrillation. An estimated 15% of strokes occur in people with atrial fibrillation, a type of heart disease. 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 break off and block a cerebral artery (causing ischemic stroke). Atrial fibrillation is a treatable medical condition. People with this form of heart disease should routinely see a cardiologist (a physician who specializes in care of the heart) and follow his or her treatment recommendations.
- Carotid Artery Stenosis. The carotid arteries are located in the neck and deliver blood to the brain. As mentioned previously, plaques can develop in these arteries, causing narrowing and decreased blood flow. Also, pieces of plaques that break off block blood vessels in the brain, can cause an ischemic stroke. Approximately 15% of individuals with ischemic stroke also have carotid artery stenosis. If severe, the carotid artery stenosis can be treated in order to decrease the chance of stroke.
- Diabetes. Diabetes is a disease in which the body does not produce or properly use insulin, a hormone that is needed to convert sugar, starches and other food into energy. As a result, the blood sugar levels of someone with diabetes are too high. Having diabetes raises a person's stroke risk significantly (diabetics are 3x more likely to have strokes than non-diabetics). Some research suggests that the uncontrolled blood sugar in diabetics makes the interior walls of their arteries more "sticky" (i.e., more apt to grab and hold on to loose particles). Because their arteries are more sticky, individuals with diabetes are more likely to experience the buildup of plaques and subsequent blood clots that can lead to ischemic stroke. Diabetes is also associated with hypertension and obesity, which further increase stroke risk.
- 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 (e.g., eggs, meat and dairy products). While some cholesterol is necessary for the body, too much cholesterol (either because of genetics or diet) increases the chance of ischemic stroke.Cholesterol and blood are "immiscible", meaning they cannot mix together (like oil and water). As a result, excess cholesterol in the blood stream tends to clump together, attach to artery walls, and form plaques, in a disease process known as arteriosclerosis. Over time, these plaques block blood vessels, and/or break off and lodge in an artery feeding the brain, causing stroke.
- 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 provide the body with a constant supply of oxygen.
- Alcohol Intake. People who drink alcohol excessively are more likely to have a stroke. Drinking alcohol can also cause high blood pressure, which in turn, raises stroke risk. However, some research suggests that light to moderate amounts of alcohol (up to 1 drink per day) might be protective against stroke. These studies are preliminary, so discuss your medical history and personal risk factors with your doctor before increasing your alcohol intake.
- Obesity. Some research suggests that mid-life obesity (defined as a Body Mass Index, or BMI of 30 or greater) is associated with heightened stroke risk for men, even when other risk factors (e.g., stress, smoking, exercise, diabetes or high blood pressure) are removed from consideration. A BMI is a calculation of the ratio of your weight to height. To calculate your current BMI, click here.
- Sedentary Lifestyle. Physical inactivity directly contributes to many of the risk factors associated with stroke described above, including obesity, diabetes, hypertension, and high cholesterol. Getting regular cardiovascular exercise is one of the best ways that you can reduce your stroke risk. Cardiovascular exercises (e.g., swimming, jogging, brisk walking, tennis, basketball, etc.) get the heart pumping for sustained periods of time, and generally leave people feeling healthier, less stressed, and more energetic. Consult your doctor before beginning any exercise program, as he or she will be in the best position to know what level of activity is best and safest for you.
There are two forms of diabetes (Type I and Type II). Both Type I (where the body fails to produce insulin) and Type II (where the body fails to properly use insulin) diabetes can be treated medically. Type II diabetes is more responsive to healthy lifestyle choices and tends to improve as people take better care of themselves. It is especially important to control your blood pressure if you have any form of diabetes. As mentioned above, a diabetic's blood pressure should be less than 130/80. Refer to our diabetes topic center (click here) for comprehensive information on the prevention and treatment of diabetes.
In January 2005 the US Department of Health and Human Services revised their recommendations for exercise. Their recommendations are as follows:
- To reduce the risk of chronic disease, you need to engage in 30 minutes of moderate intensity physical activity (e.g., brisk walking) each day.
- To help manage body weight and prevent gradual weight gain, 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.