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 80% of all strokes are ischemic, and that atherosclerosis plays an important role in most ischemic strokes. However, it is usually thrombus that finishes the job--this is what completely occludes the vessel and is the immediate cause of an ischemic stroke. A thrombus can form locally in a cerebral vessel, or a piece can break off and travel to the brain as an embolus. Therefore, other important risk factors are conditions that promote thrombus formation in locations where it can affect the brain.

Combination of risk factors for stroke
Each risk factor described in this module is associated with an increase in stroke risk, but to varying degrees. Although an increase in the number of risk factors corresponds directly with a further increase in stroke risk, the relationship is not linear.