Stroke is the third leading cause of death in developed countries (behind coronary heart disease and cancer). The consequences of a stroke are often devastating. About 25% of sufferers die as a result of the stroke or its complications, and almost 50% have moderate to severe health impairments and long term disabilities, including partial paralysis and depression. Stroke is the leading cause of serious disability in the United States. Only 26% recover most or all normal health and function.
A stroke is defined as the sudden development of neurological symptoms usually caused by a decreased blood flow to the brain. Strokes often occur abruptly with the following symptoms:
¥ Sudden trouble standing or walking, dizziness, loss of balance or coordination.
¥ Sudden numbness of the face, arm or leg weakness, especially on one side of the body.
¥ Sudden confusion, trouble speaking or underÂstanding.
¥ Sudden trouble seeing with one or both eyes.
¥ Sudden, severe headaches with no known cause.
Other important, but less common stroke symptoms include:
¥ Sudden nausea, fever and vomiting which is distinguished from a viral illness by the speed of onset (minutes or hours instead of several days)
¥ Brief loss of consciousness or a period of decreased consciousness (fainting, confusion, convulsions or coma)
As with almost all cardiovascular disease, strokes are generally the result of several underlying diseases which work to stop or reduce the flow of blood to the brain, causing disability or death.
An ischemic stroke is caused by a blood clot blocking, or Òplugging,Ó a blood vessel. An ischemic stroke can be caused by a blood clot that forms inside the artery of the brain (a thrombotic stroke), or by a clot that forms somewhere else in the body and travels to the brain (an embolic stroke).
The risk factors for thrombotic strokes are the presence of hypertension, atherosclerosis, high LDL-cholesterol, excessive blood clotting factors (such as fibrin and fibrinogen), heart valve defects, diabetes, and aging. High serum levels of homocysteine, fibrinogen and/or C-reactive protein may be the strongest predictive risk factors.
Uncontrollable Risk Factors
Increasing age. The chance of having a stroke more than doubles for each decade of life after age 55. While strokes are common among the elderly, substantial numbers of people less than 65 also have strokes.
Gender. Overall, men have about a 19% greater chance of a stroke than women. Among people under age 65, the risk for men is even greater when compared to that of women.
Family history. The chance of a stroke is greater in people who have a family history of strokes.
Race African-Americans have a much higher risk of death and disability from a stroke than Caucasians, in part because African- Americans have a greater incidence of high blood pressure.
Diabetes mellitus. Diabetes is an independent risk factor for stroke and is strongly correlated with high blood pressure. While diabetes is treatable, having it still increases a personÕs risk of a stroke. People with diabetes often also have high cholesterol and are overweight, increasing their risk even more.
Controllable Risk Factors
High blood pressure. High blood pressure is the most prominent risk factor for stroke. In fact, stroke risk varies directly with blood pressure. More widespread treatment of high blood pressure is a key reason for the decline in the death rates for strokes.
Heart disease. A diseased heart increases the risk of a stroke. In fact, people with heart problems have more than twice the risk of a stroke as those with hearts that work normally. Atrial fibrillation (the rapid, uncoordinated beating of the heartÕs upper chambers), in particular, raises the risk for stroke. Heart attack is also the major cause of death among survivors of a stroke.
High cholesterol. High cholesterol can directly and indirectly increase stroke risk by clogging blood vessels and putting people at greater risk of coronary heart disease, another important stroke risk factor.
Sleep disordered breathing. Sleep apnea is a major cardiovascular and stroke risk factor increasing blood pressure rates which may cause stroke or heart attack. Studies also indicate that people with sleep apnea develop dangerously low levels of oxygen in the blood while carbon dioxide levels rise, possibly causing blood clots or even strokes to occur. Diagnosing sleep apnea early may be an important stroke prevention tool.
Prior stroke. The risk of a stroke for someone who has already had one is several times that of a person who has not.
Carotid artery disease. The carotid arteries in your neck supply blood to your brain. A carotid artery damaged by atherosclerosis (a fatty buildup 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 health care provider may hear an abnormal sound in your neck, called a bruit, when listening with a stethoÂscope.
Transient ischemic attacks (TIAs) are Òmini-strokesÓ that produce stroke like symptoms, but no lasting damage. They are strong predictors of a stroke. A person who has had one or more TIAs is almost 10 times more likely to have a stroke than someone of the same age and sex who hasnÕt. TIAs are extremely important stroke warning signs. DonÕt ignore them!
High red blood cell count. A moderate or marked increase in the red blood cell count is a risk factor for stroke. The reason is that more red blood cells thicken the blood and make clots more likely.
Cigarette smoking. In recent years studies have shown cigarette smoking, including secondhand cigarette smoke, to be an important risk factor for stroke. The nicotine and carbon monoxide in cigarette smoke damage the cardiovascular system in many ways. The use of oral contraceptives combined with cigarette smoking also greatly increases stroke risk.
Excessive alcohol intake. Excessive drinking (an average of more than 1 drink per day for women and more than 2 drinks per day for men) and binge drinking can raise blood pressure; contribute to obesity, high triglycerides, cancer, and other diseases; and cause heart failure, leading to stroke.
Weight. Excess weight puts a strain on the entire circulatory system. It also makes people more likely to have other stroke risk factors such as high cholesterol, high blood pressure and diabetes.
Other potential risk factors
Geographic location. Stroke is more common in the southeastern United States than in other areas. These are the so called Òstroke beltÓ states. The age adjusted death rates from a stroke are much higher in these states than in the rest of the country.
Season and climate. Stroke deaths occur more often during periods of extremely hot or cold temperatures.
Socioeconomic factors. There is some evidence that people of lower income and educational levels have a higher risk for stroke.
Certain kinds of drug abuse. Intravenous drug abuse carries a high risk of stroke from cerebral embolisms. Cocaine use has been closely related to strokes, heart attacks, and a variety of other cardiovascular complications. Some of them have been fatal even in first time cocaine users.
Blood pressure For the last 50 years, medical doctors have concentrated on controlling blood pressure as the primary method of preventing stroke. As you can see, there are several other mechanisms involved. Assessing the status of the blood clotting system through accurate lab testing is central to assessing the risk of stroke.
Fibrinogen levels are useful since fibrinogen is converted into fibrin under the influence of thrombin. Fibrinogen is often elevated after acute trauma or illness, inflammation, and as a side effect of birth control pills.
Prothrombin time (PT) evaluates the time it takes for a clot to form after thromboplastin and calcium are added to the patientÕs plasma. Normal values are between 11 and 13 seconds. Prothrombin time is commonly used to monitor Coumadin therapy.
The International Normalization Ratio (INR) is a new standard that has been developed to replace the prothrombin time. The target INR is 2.5, with a range of 2 to 3. A target of 2 with a range of 1.6 to 2.5 may be used for those at high risk.
The following markers may be predictive for the risk of stroke:
Triglyceride levels have been found to be a predictor of myocardial infarction and elevated serum triglycerides have been specifically tied to the occurrence of atherothrombotic stroke and transient ischemic attacks.
Homocysteine levels has been shown to be a risk factor for cardiovascular disease, including atherosclerosis, heart attack, and stroke.
C-reactive protein (CRP) is a sensitive marker of inflammation in the body. Inflammation may be a crucial factor in atherosclerosis and is considered to be a strong predictor of myocardial infarction and stroke.
In addition, overall cardiovascular risk should also be assessed with the following lab tests:
Total, HDL and LDL cholesterol levels have been associated with cardiovascular risk for well over 40 years.
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