According to the National Stroke Association, 5 to 14 percent of people who have had a stroke will have another within one year. After five years, 24 to 42 percent of stroke patients will have had a second stroke. Uncontrollable predictors of first-time and recurrent strokes include being over age 55, being a man, being African-American, being a diabetic and being related to a stroke patient. Controllable causes include blood pressure variability, high cholesterol, atrial fibrillation and hyperthyroidism.
Hypertension
It has been known for some time that hypertension, or high blood pressure, is a major cause of first-time and recurrent stroke. Hypertension may add pressure on the brain's blood vessels, causing them to burst. This kind of stroke is also known as a brain hemorrhage. However, four studies published in "The Lancet" and "The Lancet Neurology" in March 2010 by Oxford medical researcher Peter Rothwell show that blood pressure variability is, in fact, a greater risk factor than high blood pressure. Variation in blood pressure can, independent of average blood pressure, lead to a stroke. Patients at risk of developing a stroke usually have episodic hypertension. On average, their levels may be normal, but during the hypertension attacks, there is a significant chance of clot formation or a bursting of blood vessels. The researchers also found that some stroke medications may increase the risk of a stroke, because even if they lower average blood pressure levels, they may increase the likelihood of episodic hypertension.
High Cholesterol
High levels of low-density lipoprotein, or "bad," cholesterol increase the risk of both first-time and recurrent strokes. A recent study published in the March 11, 2008, issue of "Neurology," however, show that other forms of cholesterol can make certain kinds of strokes more likely to occur. Based on a meta-analysis of medical records of 1,049 stroke patients, the research team found that high levels non-high-density-lipoprotein, or "neither good nor bad," cholesterol and triclycerides were likely to lead to a stroke in the main artery leading into the brain. High levels of bad cholesterol, while still a major factor in heart disease and other kinds of stroke, did not put people at greater risk of developing this particular kind of stroke.
Atrial Fibrillation
Atrial fibrillation is a common form of cardiac arrhythmia in which random electrical impulses from the atria, structures in the heart, disrupt the heart's normal rhythm, leading to an irregular heart beat. The condition, which affects three million people in the U.S., is a major cause of first-time and recurrent ischemic stroke. In ischemic stroke, a clot blocks blood flow to a particular area of the brain. Atrial fibrillation can be difficult to diagnose, as it tends to occur very intermittently, especially in the beginning phases. However, researchers from the Biomedical Engineering at Worcester Polytechnic Institute have discovered a new method to diagnose the condition, according to Innovations Reports, May 5, 2010. The method detects increased beat-to-beat variability and can detect atrial fribrillation with 95-percent accuracy.
Hyperthyroidism
Adults between 18 and 44 with an overactive thyroid are 44 percent more like to get a first-time or recurrent stroke compared to controls, according to a study published in the April issue of "Stroke". The researchers came to these results after adjusting for factors known to influence a person's risk of stroke, including hypertension, diabetes and heart disease. Hyperthyroidism is a hormonal disorder that causes sweating, weight loss, irritability, nervousness and increased heart rate. The researchers speculate that the irregular heart rhythm associated with hyperthyroidism may be a possible route from hyperthyroidism to stroke.
References
- Science Daily: Variability as Well as High Blood Pressure Holds High Risk of Stroke
- "Neurology"; Association of serum lipid indices with large artery atherosclerotic stroke; Bang, et al.; March 11, 2008
- Innovation Report: Detection of potentially deadly atrial fibrillation dramatically improved by new algorithm
- "Stroke"; Hyperthyroidism and Risk of Ischemic Stroke in Young Adults; Sheu, et al.; April 2010
- National Stroke Association: Recovery after Stroke: Recurrent Stroke
