Risk Factors for Stroke
High Blood Pressure
High blood pressure is serious business. Many people do not know they have high blood pressure. Allowed to run unchecked, it can cause many health problems, including heart attack, stroke, kidney damage, and blindness. On average, people with uncontrolled high blood pressure are seven times more likely to have a stroke.
A high cholesterol level contributes to stroke risk. Research has shown that the danger from cholesterol comes from a dietary intake of foods that contain high levels of cholesterol. Foods high in saturated fat and cholesterol, like meats, eggs, and dairy products, can increase the amount of total cholesterol in the body, contributing to the risk of atherosclerosis and thickening of the arteries.
There are two types of diabetes, Type 1 and Type 2. Type 1 diabetes, formerly known as juvenile diabetes, usually affects children and young adults (less than 30 years of age). In this case, cells in the pancreas no longer produce insulin, so people must take insulin throughout their lives. Maintaining a healthy weight and eating a healthy diet are important. Type 2 diabetes is more common, and usually occurs in people over 40 years of age. Type 2 diabetes makes up about 90 percent of the cases of diabetes in the United States. Though the pancreas still produces insulin, not enough is produced, or the body fails to use it properly, causing diabetes to develop. Some patients can manage this type of diabetes in the early stages with lifestyle changes, such as exercise and diet. Others may need to take an oral diabetes medication and some must take insulin.
Doctors have long known people with type 2 diabetes have an increased risk of dying from cerebrovascular disease, which is the number one cause of strokes. Studies have also shown a high rate of cardiovascular disease among people with both types of diabetes, but few studies have looked specifically at the risk of cerebrovascular disease in those with type 1 diabetes. Moderate exercise, a low-fat, low-calorie diet, weight loss, not smoking and control of blood glucose and blood pressure are important in reducing your chances of having a stroke, heart and blood vessel problems. Your healthcare provider should check your blood pressure and cholesterol levels and recommend treatment when these are not controlled by lifestyle changes alone.
Carotid artery disease
The carotid arteries in your neck supply blood to your brain. A carotid artery damaged by atherosclerosis (a fatty build-up of plaque in the artery wall) may become blocked by a blood clot, which may result in a stroke. If you have a diseased carotid artery, your doctor may hear an abnormal sound in your neck, called a bruit, when listening with a stethoscope, although even if a bruit is not evident, plague may still be present. Surgery (carotid endartectomy) or stenting (placement of a device that holds the artery open) may be necessary if the narrowing or stenosis in the carotid arteries is very severe. This procedure may be used on the carotid arteries or the arteries in the posterior circulation of the brain.
Many patients with carotid stenosis do not have symptoms. This is known as asymptomatic carotid disease. Despite the lack of symptoms, these persons may still be at a high risk for stroke depending on the degree of blockage in the carotid arteries. The tests that your primary care physician may order will provide information regarding the presence and amount of stenosis. These tests include:
- Doppler ultrasound - this is a non-invasive test in which ultrasound waves are used to reconstruct an image of the carotid arteries and the status of blood flow through the artery.
- MRA - Magnetic Resonance Imaging (MRI) and Magnetic Resonance Angiogram (MRA) employ magnetic fields to generate an image of the head and neck. The arteries in the neck and brain can be visualized and blockage detected.
- Angiography - Angiography is performed using regular X-rays. Pictures are taken while contrast dye is injected directly into the artery. The resulting angiogram is the most accurate way of looking at arteries in the neck, head and brain, and provides information that cannot be obtained with other tests.
Atrial fibrillation is a rapid uncoordinated generation of electrical impulses by the atria of the heart. Usually, the electrical impulse for contraction of the heart begins with an impulse from the sinoatrial (SA) node in the right atria of the heart, conducted via the atria to the atrioventricular (AV) node, and on to the ventricles of the heart. With atrial fibrillation, the AV node is activated irregularly and commonly very rapidly. The most serious side effect of atrial fibrillation is stroke. Half of all strokes associated with atrial fibrillation are major and disabling. The association of stroke with atrial fibrillation has been known since 1658. Depending on the presence of additional risk factors, the rate of stroke from atrial fibrillation can exceed 8 percent per year. Currently, strokes are best prevented by the careful use of Coumadin® or warfarin.
Sickle Cell Anemia
Sickle Cell Disease (SCD) is a group of inherited red blood cell disorders. Normal red blood cells are round like doughnuts, and they move through small blood tubes in the body to deliver oxygen. Sickle red blood cells become hard, sticky and shaped like sickles used to cut wheat. When these hard and pointed red cells go through the small blood tube, they clog the flow and break apart. This can cause pain, damage and a low blood count, or anemia. Seventeen percent of all SCD patients suffer a stroke. Of all people with sickle cell anemia, children between age five and 16 have the highest stroke risk. Children with sickle cell disease are 300 times more likely than normal children to have a stroke. Of the children who had a stroke and survived, 70 percent will have a second stroke and it usually occurs within 36 months of the first stroke. The most common pathology leading to stroke in SCD patients is cerebral thrombosis, followed by intracerebral hemorrhage. The typical infarction in normal adults is intracranial hemorrhage. Some researchers speculate this difference in pathology in children is due to the increased cerebral blood flow, a consequence of higher oxygen demands.
Cigarette smoking is the most powerful modifiable stroke risk factor. Smoking almost doubles a person's risk for ischemic stroke, independent of other risk factors, and it increases a person's risk for subarachnoid hemorrhage by up to 3.5 percent. Smoking increases the risk of stroke by promoting atherosclerosis and increasing the levels of blood-clotting factors, such as fibrinogen. In addition to promoting conditions linked to stroke, smoking also increases the damage that results from stroke by weakening the endothelial wall of the cerebrovascular system. This leads to greater damage to the brain from events that occur in the secondary stage of stroke.
While it has been suspected for some time that being overweight could potentially increase a person's chances of a stroke, a study published in the December 9, 2002, issue of the Archives of Internal Medicine offers some of the first concrete evidence that as a man's weight increases, so does his chance of suffering from a stroke.
The risk of stroke for someone who has already had one is many times that of a person who has not.
There are certain blood disorders in which the blood is more likely than normal to form blood clots and these are known as hypercoaguable states. These conditions may be associated with auto-immune diseases like lupus and are most often treated with blood thinners such as warfarin.
Stroke Factors Specific to Women
The latest data show that, overall, the incidence and prevalence of stroke are about equal for men and women. However, at all ages, more women than men die of stroke.
Studies have found that migraine or severe headache is a risk factor for stroke in both men and women, especially before age 50. About 19 percent of all strokes occur in people with a history of migraines. Migraine with aura carries a higher risk for stroke than without auras. Interestingly, a 2001 study reported that in people who experienced migraine-related stroke, the frequency of migraines declined afterward.
The actual risk itself for migraineurs is low, however, one study suggests specific risk factors for younger women with migraines, particularly those with auras:
- Taking high-estrogen oral contraceptives (OCs). (Whether progesterone-alone contraceptives carry any risk is unknown.)
In migraineurs who take OCs, the risk increases with one or more of the following:
- High blood pressure.
- Women with migraines had a 2.7 percent risk of stroke, with the time of greatest risk between the ages of 45 and 65.
- Men with migraines had a 4.6 percent risk and their greatest time of risk was before age 45.
Women in the postpartum period are more likely to experience stroke than women of childbearing age who are not pregnant, Emory neurologist Barney J. Stern and others reported recently in a New England Journal of Medicine article, "Pregnancy and the Risk of Stroke." The study is the most comprehensive to date evaluating pregnancy stroke risk. Researchers evaluated the occurrence of stroke during 234,014 pregnancies during 1988 and 1991. They report that of 192 strokes caused by cerebral infarctions, 17 were related to pregnancy, and that of 62 strokes caused by intracerebral hemorrhages among the women begin studied, 14 were related to pregnancy. The researchers estimate that about 8.1 strokes occur during every 100,000 pregnancies.
Menopause/Hormone Replacement Therapy
Combined hormone replacement therapy (HRT) increased the risk of stroke for postmenopausal women of all ages, whether or not they had hypertension. Researchers reported these findings, which are based on women studied in the Women's Health Initiative, at the American Stroke Association's 28th International Stroke Conference. The American Stroke Association is a division of the American Heart Association.
Managing Risk Factors for Stroke
The risk of having a stroke increases with age, but there are several ways you can reduce your risk for stroke.
- Quit smoking.
- Keep your cholesterol low.
- Monitor and control high blood pressure.
- Monitor and control diabetes
- Exercise and control your weight.
- Limit your alcohol use.
- Calm down and keep stress low.
Visit your doctor regularly to find out if you have high blood pressure, diabetes, heart disease or carotid artery disease.