Stroke Causes & Risk Factors

By Tiffany Tseng. May 7th 2016

What Causes a Stroke?

Strokes can happen when the blood supply to the brain is blocked off, or when a blocked blood vessel in the brain hemorrhages. In both cases, the surrounding tissues and part of the brain can become severely damaged. Such disturbances in the brain will render the affected area unable to function, and can be deadly.

In an ischemic stroke, a clot or thrombus is created through a buildup of plaques on the walls of arteries. Such plaque deposits are usually created by high concentrations of low-density lipoproteins (LDL) in blood cholesterol. When too much plaque accumulates, the diameter of the artery severely decreases. The artery also becomes hardened and inflexible, resulting in decreased blood flow to the brain. Sometimes, a blood clot may break off from an already-formed plaque in other parts of the body and travel to the brain, where it becomes lodged in the narrower blood vessels.

In a hemorrhagic stroke, a blood vessel ruptures and fills the space between the brain and the skull with blood. Brain cells beyond the hemorrhage site are also deprived of oxygen and glucose. Hemorrhaging can be caused by a number of things, including high blood pressure (hypertension), weak spots in the blood vessel (aneurysm) or other forms of trauma. In both ischemic and hemorrhagic strokes, brain cells become damaged or die due to the lack of oxygen and nutrients that it normally receives from red blood cells.

What Are the Risk Factors?

While strokes can happen to anyone at any time, there are several risk factors that may place an individual more at risk than others. Generally, the risk factors are grouped into three categories:

Prior Medical Conditions

Individuals who had prior blood-related health conditions are more at risk than others. Increased blood cholesterol, for example, is a common risk factor. When the fatty deposits from cholesterol build up on the interior of blood vessel walls, they narrow the diameter of blood vessels and increase the chances of a stroke. High blood pressure, usually caused by excessive salt intake, smoking and alcohol abuse, also places an individual at higher risk for brain hemorrhaging. Sickle cell anemia, a blood disorder that affects mostly people of African descent, are also linked to ischemic strokes, as the sickle blood cells can clog blood flow to the brain. Diabetic individuals are also more at risk, since sugar buildup in the blood can also lead to hypertension and high cholesterol.

Similarly, heart and artery diseases will place an individual at more risk for a stroke. Coronary heart disease (CAD), which is characterized by fatty plaques blocking heart arteries, is such an example. Heart conditions, such as enlarged heart chambers, irregular heartbeat and defected heart valves, can also increase risks. Individuals who are severely overweight are also more prone to strokes, since obesity is almost always correlated with heart diseases.

Individuals who had previous strokes or transient ischemic attacks are more prone to recurrent cases than people who never had stroke. Therefore, it is important to consult a physician for treatment options if you have one or more medical conditions that put you at risk for a stroke.


Certain behavioral habits increase an individual's susceptibility to stroke, as they may set the platform for cardiovascular diseases. For example, excessive alcohol use can lead to hypertension and hardening of the arteries, due to increased cholesterol. A poor diet with high levels of fat, cholesterol and sodium will also result in high blood pressure and plaque formation along artery walls. Cigarette smoking and smoke inhalation from secondhand smoke will increase the body's level of carbon monoxide. This component, found in all cigarette smoke, reduces the amount of oxygen carried by red blood cells and speeds up the hardening of the arteries. An inactive lifestyle may lead to excessive weight gain, which leads to hypertension and high cholesterol. Abuse of hard drugs, such as cocaine, heroin or amphetamines, are also responsible for stroke in younger populations. By making simple lifestyle alterations, such as an active life and a healthy diet, can significantly decrease risk factors.


Heredity also plays a role in determining the susceptibility to stroke, since several genetic disorders place an individual at higher risk for stroke. For example, sickle cell anemia is a blood disorder characterized by sickle-shaped red blood cells that (due to their shape) are prone to clog arteries. Demographically, Africans, Hispanics and Native Americans are more prone to stroke than are Caucasians or Asians.

Genes often determine the development of medical conditions that can lead to a stroke, including hypertension, heart disease, diabetes and vascular conditions. Thus, individuals who have a family history of stroke also have increased chances of stroke. Men experience higher risks for stroke than women do, and older people have higher chances than younger people to have a stroke.

While there is no way to predict when a stroke may occur, having routine physical exams with your doctor can help identify already-present risk factors and set preventative treatment plans to avoid strokes from taking place.

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