Some people are at a higher risk for stroke than others. Some of these risk factors cannot be changed, such as the persons' age, gender, race/ethnicity, and family history of stroke. However, there are important risk factors that can be changed to reduce a person's change of having a stroke.
People with more than one risk factor have what is called "amplification of risk." This means that the multiple risk factors compound their destructive effects and create an overall risk greater than the simple cumulative effect of the individual risk factors.
It is possible to dramatically reduce these risks through healthier lifestyle choices or medications. In fact, since 1950, there has been about a 60% decline in the mortality rate from stroke that are attributed to an increasing awareness and control of stroke risk factors.
Modifiable Risk Factors
The most important modifiable risk factors for stroke are as follows:
- Hypertension increases the risk of having a stroke 2-4 times before age 80. After the age of 80, the increased risk from hypertension declines and other risk factors become more important.
- Hypertension promotes atherosclerosis and causes mechanical damage to the walls of blood vessels.
- Blood pressure medications, such as thiazide diuretics and angiotensin-converting enzyme (ACE) inhibitors, can reduce the risk of stroke by 30 to 40 percent.
- Early treatment is essential. among older people with normal blood pressure, prior mid-life hypertension increases stroke risk up to 92%.
- Guidelines from the Centers for Disease Control and Prevention recommend a target blood pressure of less than 140/90 mm Hg.
- Smoking causes about a two-fold increase in the risk of ischemic stroke and up to a four-fold increase in the risk of hemorrhagic stroke.
- Smoking promotes atherosclerosis and aneurysm formation, and stimulates blood clotting factors.
- Stroke risk decreases significantly two years after quitting smoking and is at the level of nonsmokers by five years.
- In terms of stroke and cardiovascular disease risk, having diabetes is the equivalent of aging 15 years.
- In diabetes, glucose is not efficiently taken up by the body's cells and accumulates in the blood instead, where it can damage the vascular system.
- Hypertension is common among diabetics and accounts for much of their increased stroke risk.
- Blood pressure medications, dietary changes, and weight loss can lower stroke risk.
- Controlling blood sugar appears to reduce the risk of recurrent stroke.
Physical inactivity and obesity
- Waist-to-hip ratio equal to or above the median (mid-value for the population) increases the risk of ischemic stroke three-fold.
- Obesity is associated with hypertension, diabetes, and heart disease.
- While no clinical studies have tested the effects of exercise or weight loss on stroke risk, both tend to reduce hypertension and boost cardiovascular health.
Atrial fibrillation (AF)
- Atrial fibrillation affects fewer than 1% of people under age 60, but is more prevalent in older people. It is responsible for one in four strokes after age 80, and is associated with high mortality and disability.
- AF refers to irregular contraction of the atrium - the chamber where blood enters the heart. aF can lead to blood stagnation and increased clotting.
- Warfarin, a blood-thinning medication, can reduce the risk of stroke in people with aF. People under age 60 with aF and no other stroke risk factors may benefit from aspirin. Importantly, pacemakers have no effect on the risk of stroke associated with AF.
- High-density lipoprotein (HDL) cholesterol is generally considered protective against ischemic stroke. Low-density lipoprotein (LDL) cholesterol, when present in excess, is considered harmful.
- LDL and HDL are needed to carry cholesterol (a fatty substance) through the blood (made up mostly of water), and deliver it to cells. because LDL delivers cholesterol to cells throughout the body, excess LDL can cause cholesterol to build up in blood vessels, leading to atherosclerosis. HDL sends cholesterol to the liver to be eliminated.
- Clinical trials have shown that cholesterol-lowering drugs known as statins reduce the risk of stroke. However, some studies point to only a weak association between stroke and cholesterol, and there is speculation that statins reduce stroke risk by acting through some unknown mechanism.
Other Modifiable Risk Factor
- Others risk factors include heavy alcohol consumption and illicit drug use.
Unmodifiable Risk Factors for Stroke
Stroke and Age
It is a myth that stroke occurs only in elderly adults. In fact, people in all age groups can experience a stroke, including fetuses still in the womb. However, it is true that older people have a higher risk for stroke than the general population and that the risk for stroke increases with age.
For every decade after the age of 55, the risk of stroke doubles, and two-thirds of all strokes occur in people over 65 years old. People over 65 also have a seven-fold greater risk of dying from stroke than the general population. And the incidence of stroke is increasing proportionately with the increase in the elderly population.
Family History of Stroke
Stroke seems to run in some families. Several factors might contribute to familial stroke risk. Members of a family might have a genetic tendency for stroke risk factors, such as an inherited predisposition for hypertension or diabetes. The influence of a common lifestyle among family members could also contribute to familial stroke.
Vascular malformations that cause stroke may have the strongest genetic link of all stroke risk factors. A vascular malformation is an abnormally formed blood vessel or group of blood vessels. One genetic vascular disease called CADASIL, which stands for cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy. CADASIL is a rare, genetically inherited, congenital vascular disease of the brain that causes strokes, subcortical dementia, migraine-like headaches, and psychiatric disturbances. CADASIL is very debilitating and symptoms usually surface around the age of 45. Although CADASIL can be treated with surgery to repair the defective blood vessels, patients often die by the age of 65. The exact incidence of CADASIL in the United States is unknown.
Reference: The National Institute of Neurological Disorder and Stroke.