Causes
An ischemic stroke is the result of blockage in blood flow to the brain caused by a blood clot. The buildup of plaque in the artery wall (atherosclerosis, or "hardening of the arteries") is an underlying cause for many ischemic strokes.
Atherosclerosis is a process in which fatty deposits (plaques) build up inside the blood vessels of the body, particularly in the carotid arteries of the neck, the coronary arteries of the heart, and the arteries of the legs. Atherosclerotic plaques can lead to a stroke by causing blockage of blood flow, or by dislodged plaque material (emboli) that can travel to the brain.
A hemorrhagic stroke is caused by bleeding into the brain (intracerebral hemorrhage) or bleeding around the brain (subarachnoid hemorrhage), which results from the breakage of a blood vessel. Brain hemorrhages may result from uncontrolled high blood pressure, and, in some cases, can be caused by structural problems within the blood vessels (e.g., aneurysms or vascular malformations).
There are numerous risk factors that can cause a stroke.
Factors you can't control are:
- age: The risk of stroke increases with advancing age.
- ethnicity: People of American Indian, African, Hispanic, and South Asian descent have greater rates of high blood pressure and diabetes. These conditions increase the risk of stroke.
- family history: The risk of stroke may be higher if a parent or sibling has had a stroke before the age of 65.
- prior stroke or transient ischemic attack (TIA): Up to one-third of people who survive a first stroke or TIA will have another stroke within 5 years.
Factors you can control are:
- high blood pressure
- heart disease or atrial fibrillation (irregular heartbeat)
- cigarette smoking
- diabetes
- high cholesterol
- physical inactivity
- high alcohol intake (more than 2 drinks per day)
Other factors that can lead to a stroke are:
- other medical conditions such as amyloid angiopathy and antiphospholipid antibody syndrome
- use of illicit drugs such as cocaine or LSD
- some medications, such as tamoxifen*, phenylpropanolamine, and thrombolytics
Oral contraceptive use, hormone replacement therapy, pregnancy and childbirth in women with preexisting medical conditions may increase the risk of stroke in specific cases, but there is no conclusive evidence to date. Talk to your doctor about risk factors that may be relevant to you and your risk of stroke.