Risk Factors

Obesity and Metabolic Syndrome

Obesity may increase the risk for both ischemic and hemorrhagic stroke independently of other risk factors that often co-exist with excess weight, including insulin resistance and diabetes, high blood pressure, and unhealthy cholesterol level. Weight that is centered around the abdomen (the so-called apple shape) has a particularly high association with stroke, as it does for heart disease, in comparison to weight distributed around hips (pear-shape).

Obesity is particularly hazardous when it is one of the components of metabolic syndrome. This syndrome is diagnosed when three of the following conditions are present: abdominal obesity, low HDL cholesterol, high triglyceride levels, high blood pressure, and insulin resistance. Because metabolic syndrome is a pre-diabetic condition that is significantly associated with heart disease, people with this syndrome are at increased risk for stroke even before diabetes develops.

Cholesterol and Other Lipids

Although an unhealthy balance of cholesterol and other lipids (fatty compounds) plays a major role in heart disease, its role in stroke is less clear. Different lipids may have different effects:

Ischemic Stroke. The effects of high total cholesterol and LDL levels on stroke are not clear. One study suggested that the risk for ischemic stroke increases when total cholesterol is above 280 mg/dL. HDL (the so-called good cholesterol) may protect against ischemic stroke (although statins have little effect on HDL).

Hemorrhagic Stroke. HDL may reduce the risk for hemorrhagic stroke (bleeding in the brain). People with overall cholesterol levels below 180 mg/dL, however, may be at risk for hemorrhagic stroke, particularly if they also have high blood pressure. This is a far less common stroke, however, than ischemic stroke.

In any case, reducing cholesterol is extremely important in anyone with heart disease and abnormal lipid levels.

Genetic and Inborn Factors

Genetics may be responsible for many of the causes of stroke. Studies indicate that a family history of stroke, particularly in one's father, is a strong risk factor for stroke.

Genetics and Subarachnoid Hemorrhage. Genetic factors account for between 7 - 20% of cases of subarachnoid hemorrhage. Ruptured aneurysms that occur in such patients tend to happen at an earlier age, are usually smaller, and are more apt to recur than in those without an inherited condition. A study of people who had suffered subarachnoid hemorrhages found that first-degree relatives of these stroke victims had a high lifetime risk of between 2 - 5%. Some experts recommend screening for aneurysms in people with more than one close relative who suffered a hemorrhagic stroke.