Causes of Stroke

A stroke happens suddenly and can potentially have serious and damaging repercussions. But while the visible aspects of a stroke certainly strike abruptly, behind the scenes a stroke is caused by any number of factors that slowly build over years. The good news is that the causes of stroke are well understood.

Most people who experience a stroke have more than one predisposing factor. There is also a good deal of overlap among stroke causes, as some of the causes of stroke also lead to other conditions that ultimately influence stroke risk, resulting in a vicious cycle. Most of the causes of stroke, however, are preventable or at least controllable.

Heart Disease

Heart disease is the leading cause of stroke, since every heartbeat sends blood from the heart throughout the entire body. If a blood clot forms in the heart as a result of an irregular heartbeat (arrhythmia) or heart valve disease, the clot can easily travel to the brain, obstructing blood flow and producing a stroke.

Intracranial Artery Disease

When blood vessels in the brain (cerebral vessels) become unhealthy and irregular, a blood clot can become trapped inside them, interfering with blood flow and causing a stroke. The arteries in the brain may become damaged due to high blood pressure, high cholesterol, diabetes, and smoking.

Carotid Artery Disease

The carotid arteries are the two largest and most important arteries that route blood from the heart to the brain. They can become narrow, stiff, and full of dangerous debris as a result of diseases such as hypertension, diabetes, and high fat and cholesterol levels. This can cause the blood supply to the brain to become compromised or, in severe situations, completely blocked.

Another way that carotid artery disease causes stroke is when the debris that builds up inside the carotid arteries becomes dislodged and travels to the brain, obstructing a cerebral vessel and causing a stroke. Surgery can help repair carotid artery disease and reduce the risk of stroke.


Chronic high blood pressure puts a strain on arteries throughout the body. Hypertension is one of the causes of intracranial artery disease and carotid artery disease as well as disease of the arteries of the heart. These conditions are all likely to develop gradually over the years if high blood pressure goes untreated.

Malignant Hypertension

Episodes of extreme hypertension can occur suddenly, especially as a result of untreated hypertension or drugs. Malignant hypertension can cause a stroke in a few ways. It causes blood vessels to spasm, obstructing blood flow, and causing a stroke. Malignant hypertension can also cause a blood vessel to leak or burst, resulting in a hemorrhagic stroke. Defective blood vessels in the brain are prone to rupture in the setting of malignant hypertension.


Diabetes is a condition that makes it difficult for the body to maintain a normal blood sugar level. When someone with unmanaged diabetes has recurrently high blood glucose levels, the resulting metabolic changes in the body can damage arteries, causing intracranial disease, carotid artery disease, and disease of the arteries of the heart. All this substantially increases the chance of having a stroke.


Smoking is one of the most preventable causes of stroke. The chemicals in cigarette smoke are well known to be toxic to the lungs. But most people do not realize that smoking injures the inner lining of blood vessels throughout the body, making them jagged, stiff, and narrow. This makes it likely for blood clots to form and get stuck inside the arteries. Smoking contributes to heart disease, intracranial artery disease, and carotid artery disease.

High Cholesterol & Triglyceride Levels

High cholesterol is a well-known risk factor for stroke, while the role of high triglycerides as the cause of stroke is more controversial, with some studies showing an association and others not. It is presumed that the increase in cholesterol and triglycerides damage the inside of blood vessels throughout the body, making it more likely for blood clots to get stuck inside the arteries and impede normal blood flow. And the stickiness of cholesterol and fat triglycerides molecules in the blood makes it more likely that blood clots will form in the first place.

Recommended cholesterol and triglyceride levels are well-established. Levels above the recommended levels are strongly associated with stroke. The biggest controversy about blood cholesterol and fat levels lies in whether these levels are the product of diet, genetics, or something else. Even scientific research has conflicting stances, suggesting that diet has a major impact, a moderate impact, and even no impact on blood fats and blood cholesterol. Certainly, a diet rich in fresh fruits and vegetables and moderate in natural fats—as opposed to artificially produced ones—is a good rule of thumb.


Science shows that a BMI over 30 is linked to high stroke risk. Interestingly, the most consistently documented benefit of weight loss surgery is decreased risk of stroke.

Sedentary Lifestyle

To some, a lack of activity is a surprising cause of stroke. Yet, research consistently shows that inactivity causes stroke independently of obesity, high cholesterol, and hypertension. It has been proven that a moderate amount of exercise is strongly associated with stroke prevention.

Excessive Stress

Long-term anxiety and agitation alter hormones in your body, contributing to hypertension and heart disease. In fact, post-traumatic stress disorder is associated with an increased chance of having a stroke, even years after the initial source of trauma has ceased. Other stressful lifestyle factors, including long work hours, shift work, and family upheaval are also strongly correlated with an increased chance of having a stroke.


A variety of different drugs commonly abused are known to cause a stroke. Some drugs cause stroke during use, while others produce gradual physical damage to the body, causing a stroke after multiple uses. Cocaine, for example, induces sudden stroke due to its tendency to cause blood vessels to spasm abruptly, blocking blood flow to the heart or brain. Repeated use of methamphetamine, on the other hand, produces long-term damage that raises the likelihood of stroke. Chronic, heavy alcohol use has also been connected with stroke.

Blood Disorders

Blood-clotting conditions and bleeding disorders are usually hereditary. Living with a blood disorder increases the risk of ischemic stroke and hemorrhagic stroke. Blood disorders must be carefully managed under close medical supervision.


While relatively common, infections that spread throughout the body (sepsis) can alter blood flow in such a way that increases the chances of a blood clot forming anywhere in the body, including the brain.

Autoimmune Disease

Most autoimmune diseases are associated with a mildly increased risk of having a stroke. This is usually the result of an increased tendency to form blood clots and, ironically, an increased tendency to experience arterial bleeding.

Severe Systemic Disease

Severe medical conditions such as kidney failure, liver failure, and major trauma can result in dramatic alterations in bodily functions necessitating long-term intensive care treatment. The body often has difficulty in adapting to major systemic illnesses. And one of the effects of the overwhelming disruption to the body can be a stroke, which further complicates an already difficult situation.

A Word From Verywell

There are a number of well-known causes of stroke. Most of these risk factors are due to mechanisms that are well understood and that can prepare us to take preventive measures.

The majority of the causes of stroke overlap with each other and contribute to each other. That means that if you tackle one, you will simultaneously minimize one or more of the other causes of stroke. For example, taking diabetes medication to control blood glucose levels can, in turn, affect weight management, hormone levels, and other factors that often contribute to heart disease and stroke. Similarly, if you exercise to ward off stroke, it will also lend itself to the prevention of both hypertension and obesity.

Familiarizing yourself with the causes of stroke can be the best protection you have in the long-term to decrease and avoid risk. Preventing a stroke has been shown to add an average of 12.5 years to your life.

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