Risk Factors

Risk factors reflect the pathology that is responsible for the major types of strokes

Many risk factors have some role in promoting or accelerating atherosclerotic plaque formation and ulceration. This makes sense when you remember that 87% of all strokes are ischemic, and that atherosclerosis plays an important role in the majority of ischemic strokes. Flow-limiting stenosis of major extracranial or intracranial vessels caused by plaque may produce ischemia. However, it is usually thrombotic material that acutely occludes large or small intracranial vessels and is the immediate cause of ischemia. Also recall that a thrombus that threatens blood flow to the brain can form locally in a cerebral vessel itself, or it can form in more distant sites including the aortic arch, arteries in the neck, or the heart and then detach and travel as an embolus to reach the brain. Therefore other important stroke risk factors include conditions that promote formation of thrombi in these more distant locations. Hypertension is the most significant of the stroke risk factors. It is linked not only to atherosclerosis but also to lipohyalinosis (a major contributor to small-vessel ischemic strokes). Hypertension is also the major cause of intraparenchymal hemorrhage.

Some of the risk factors for stroke are potentially “modifiable.”

This means that they may be treated or controlled. In most cases, there is good evidence that treatment leads to significant reductions in the occurrence of stroke and in death from stroke. It has been estimated that if current prevention activities were uniformly performed at levels achieved by the best U.S. health care delivery systems, approximately 20% of strokes would be prevented (Circulation. 2008; 118:576; also see module 6 - Prevention and Stroke Therapy).

“Modifiable” risk factors for stroke are often separated into medical conditions which reflect the existence of underlying pathology or pathophysiology, and lifestyle-related factors which may be independent risk factors and/or contribute to one or more of these medical conditions.