Stroke occurs when part of the brain is deprived of blood, either by a blood clot or by a burst blood vessel. High blood pressure increases your risk.
A stroke occurs when part of your brain is deprived of blood. That means the brain cells don’t get the oxygen and nutrients that they need to function. If the blood supply is not restored quickly, the brain cells start to die. Dead brain cells don’t grow back. This is why it’s very important to get treatment for a stroke as soon as possible.
Strokes can happen for two main reasons. In an ischemic (iss-KEE-mick) stroke, a blood vessel is completely or partially blocked by a blood clot. The clot may form there, or may have traveled to the brain from another part of the body (such as the heart). In a hemorrhagic (hem-oh-RAH-jick) stroke, a blood vessel bursts open. This may occur because of an aneurysm (a weakening of the wall of an artery, causing it to balloon out), an abnormality in the blood vessels of the brain, high blood pressure, or other factors.
There are several common risk factors for stroke, including:
• High blood pressure
• Smoking or heavy alcohol use
• Demographics (age, race, and gender)
• Problems with the heart, such as atrial fibrillation (abnormal heart rhythm)
• Other medical conditions (such as diabetes, high cholesterol, and sleep apnea)
• Unhealthy lifestyle, including being overweight and not exercising
High blood pressure is the most common risk factor for stroke. A normal blood pressure is 120/80. The risk of stroke increases above this pressure, with the risk being higher at higher blood pressures.
Smoking is strongly associated with stroke. Even exposure to secondhand smoke increases your risk of stroke. Heavy alcohol use is also associated with stroke, although moderate alcohol use (drinking one alcoholic beverage per day) is actually associated with a decreased risk. Using certain illicit drugs, such as methamphetamines or cocaine, can also increase the risk of a stroke.
Certain risk factors for stroke are not within your control. Older people are at higher risk than younger people. Your race is also a factor, with African-Americans being at a higher risk for stroke than those of other races. Additionally, men are at higher risk for stroke than are women.
Problems with the heart may increase the risk of stroke. For example, atrial fibrillation, in which the upper chambers of the heart quiver but don’t pump any blood, can lead to the formation of blood clots in those quivering chambers. These clots can later move from the heart to the brain, where they cause a stroke.
Several other medical conditions are also associated with an increased risk of stroke, including diabetes, high cholesterol, and sleep apnea (in which the blood oxygen level drops repeatedly during sleep).
An unhealthy lifestyle also increases the risk of stroke. Being significantly overweight or obese increases your risk. Physical inactivity, regardless of your weight, is also a risk factor. Even if you’re naturally thin, it’s important that you get enough exercise (at least 30 minutes per day on most days of the week) to protect yourself from stroke and other health problems.
Centers for Disease Control and Prevention (CDC). “Stroke: About Stroke.” CDC website (2014). http://www.cdc.gov/stroke/about.htm
National Institute of Neurological Disorders and Stroke (NINDS). “NINDS Stroke Information Page.” NINDS website (2015). http://www.ninds.nih.gov/disorders/stroke/stroke.htm
Mayo Clinic Staff. “Stroke: Overview.” Mayo Clinic website (2015). http://www.mayoclinic.org/diseases-conditions/stroke/home/ovc-20117264