Stroke is a serious medical emergency caused by a depleted supply of blood to a part of the brain. There are two types of stroke - ischemic stroke and hemorrhagic stroke:

Ischemic stroke
The sudden lack of blood flow to a brain region is usually caused by a blood clot obstructing a blood vessel. This is called ischemic stroke and accounts for 80% of all strokes.

Hemorrhagic stroke
Hemorrhagic stroke occurs due to a ruptured blood vessel (usually due to an anuerysm) that causes leaking blood to accumulate and compress surrounding brain tissue.

Stroke is a preventable condition and there are several modifiable risk factors that can be altered to reduce the risk of stroke. Some factors, however, are not modifiable and will always raise the risk of stroke.

Some of the risk factors associated with stroke include:

• Age - The risk of stroke rises with age. This is mainly because all the other risk factors for stroke such as heart disease and atherosclerosis are more common in older than in younger people.
• Heart diseases such as high blood pressure, angina, atherosclerosis, coronary artery disease, mitral valve disease, cardiomyopathy, pericarditis, atrial fibrillation and cardiac arrythmias
• High levels of low density lipoprotein cholesterol or "bad cholesterol" along with low levels of high density lipoprotein cholesterol or "good cholesterol" increases the likelihood of atherosclerosis. Atherosclerosis refers to the formation of plaques within blood vessels which raises the risk of stroke.
• Diabetes
• Genetic factors - Risk factors for stroke are often hereditary. Examples include heart disease, high blood pressure and diabetes.
• Race and ethnicity - People of Asian, African or Caribbean origin are at a greater risk of stroke than other ethnicities.
• Excess alcohol intake and smoking
• Overweight and obesity
• Overactive thyroid gland