The two primary types of stroke are ischemic stroke and hemorrhagic stroke.
Ischemic stroke accounts for about 75% of all strokes and occurs when a blood clot, or thrombus, forms that blocks blood flow to part of the brain. If a blood clot forms somewhere in the body and breaks off to become free-floating it is called an embolus. This clot may be carried through the bloodstream to the brain where it can cause ischemic stroke.
Hemorrhagic stroke occurs when a blood vessel on the brain's surface ruptures and fills the space between the brain and skull with blood (subarachnoid hemorrhage), or when a defective artery in the brain bursts and fills the surrounding tissue with blood (cerebral hemorrhage). Both result in a lack of blood flow to the brain and a buildup of blood that puts too excessive pressure on the brain. Aneurysms - abnormal blood-filled pouches that balloon out from weak spots in the wall of an artery - are the most common cause of subarachnoid hemorrhage. If an aneurysm ruptures, blood spills into the space between the surfaces of the brain and skull, and blood vessels in the brain may spasm. Aneurysms are often caused or made worse by high blood pressure. A less common from of hemorrhage stroke is when an arteriovenous malformation (AVM) ruptures. AVM is an abnormal tangle of thin-walled blood vessels that is present at birth.

• Over age 55
The older one gets, the greater the chance of having a stroke. This is due to the hardening of the arteries as one grows older. The chance of having a stroke more than doubles for each decade of life after age 55.
• Male
In most age groups, men tend to have more strokes in a given year than women. However, women who are pregnant, those who are taking birth control pills and who also smoke or have high blood pressure and other risk factors will also have higher risk for stroke.
• African American, Hispanic or Asian/Pacific Islander
In African-Americans, stroke is more common and more deadly--even in young and middle-aged adults--than for any ethnic or other racial group in the United States. Scientists have found more and more severe risk factors in some minority groups and continue to look for patterns of stroke in these groups.
• A family history of stroke
There is a slightly increased chance of having a stroke if members of your immediate family have had strokes. This is particularly true if your relatives were young when they had their strokes.
• High blood pressure
This is a major risk factor for stroke. Know your blood pressure and have it checked at least once every two years. It should be lower than 120/80 mm Hg.
• High cholesterol
High cholesterol may increase stroke risk by increasing your risk for heart diseases. Fatty deposits that are caused by high cholesterol may also block normal blood flow to the brain, and cause a stroke.
• Smoking cigarettes
Cigarettes contain high levels of cadmium that causes the blood to clot activity of cells in result of blocking blood flow and damaging the blood vessels in the brain.
• Diabetes
People with diabetes tend to develop heart disease or have strokes at an earlier age than other people.
• Obesity
Study shows that even after adjusting for other stroke risk factors obesity is still associated with a greatest risk of stroke in men and women.
• Cardiovascular disease
Common heart disorders such as coronary artery disease, valve defects, irregular heart beat, and enlargement of one of the heart's chambers can result in blood clots that may break loose and block vessels in or leading to the brain.
• A previous stroke or transient ischemic attack (TIA)
A TIA (transient ischemic attack) is a "mini" stroke that lasts a short time and goes away without causing permanent damage. Recognizing and treating TIAs can reduce your risk of a major stroke. It's very important to recognize the warning signs of a TIA or stroke. Call 9-1-1 or get medical attention immediately if they occur.
• High levels of homocysteine (an amino acid in blood)
Homocysteine is a common nutrient utilized by our bodies to make proteins. But early studies found that high homocysteine levels increase a person's risk for heart disease, and subsequent studies also demonstrated that they can also increase the risk of stroke.
• Birth control use or other hormone therapy
Birth control pills contain estrogen and one of two other hormones, lynestrenol or norethisterone that increase the risk of blood clotting, which can lead to ischemic stroke especially in woman who smoke and who are older than 35.
• Heavy use of alcohol
Moderate drinking is good for your heart, but excessive drinking can raise levels of some fats in your blood causing cholesterol to build up in the arteries and blood vessels in the brain resulting in increase of the risk of stroke.

All people can take steps to lower their risk for stroke, whether they have had a stroke or not. Things you can do to lower the risk of stroke include steps to prevent and control high blood pressure, heart disease, and other chronic conditions.

Reduce high blood pressure
High blood pressure (hypertension) is the most significant risk factor for stroke. Blood pressure refers to the pressure inside the arteries. Hypertension means that the blood is exerting more pressure than is normal or healthy. Over time, this weakens and damages blood vessel walls, which can lead to cerebral haemorrhage. Hypertension may also cause thickening of the artery walls, resulting in narrowing and eventual blockage of the vessel (ischaemic stroke). In atherosclerosis (hardening of the arteries), the pressure of your pumping blood could 'hose off' debris from damaged artery walls. The circulating debris (embolism) can cause a stroke by lodging in and blocking a blood vessel of the brain. Strategies to reduce high blood pressure include:

- Check your blood pressure regularly and know your numbers.
- Maintain a healthy weight for your height.
- Exercise regularly.
- Choose a low fat, high fibre diet.
- Reduce or eliminate salt from your diet.
- Limit your alcohol intake to two or less standard drinks per day.
- Stop smoking.
- Take antihypertensive medications to help control high blood pressure.

Manage your diabetes
Diabetes is a chronic condition in which the body is unable to utilise blood sugar. A person with diabetes is around twice as likely to have a stroke as someone of the same gender and age who doesn't have diabetes. This is because the high blood sugar levels contribute to the development of atherosclerosis. It is very important that diabetes be kept under control.

Eat a healthy diet
Various studies show that diet is an important risk factor in the development of stroke. Suggestions include:

- Limit or moderate salt intake.
- Choose fresh rather than processed foods.
- Increase your intake of vegetables, fruit and whole grains.
- Cut out or reduce sugary and fatty foods.
- See a dietitian who can help you plan a well-balanced low fat, high fibre diet.

Exercise regularly
A sedentary lifestyle increases the likelihood of obesity, high blood pressure and high blood cholesterol levels. These are all important risk factors for stroke. Suggestions include:

- See your doctor for a check-up if you haven't exercised for a while.
- Choose a range of activities you enjoy.
- Contact a physiotherapist or gymnasium instructor for advice and information regarding appropriate exercise.
- Try to get moderate exercise for at least 30 minutes on (at least) five days of the week.