Epidemiology and prevention of stroke, now and in the future.

Studies of the epidemiology of stroke have greatly improved over the past 20 years because of 1) the development of new technology that improved classification of specific types of stroke (1), 2) better therapies that have reduced case fatality (1), 3) prevention of stroke (i.e., antihypertensive drug therapy) (1), and 4) health insurance, especially Medicare. Stroke cases can now be classified in epidemiology studies by type. For example, in the Framingham Study, for men aged 55-84 years, 45 percent of strokes were classified as atherosclerotic, 19 percent as cerebral embolism, 5 percent as intracerebral hemorrhage, 4 percent as subarachnoid hemorrhage, 19 percent as transient ischemic attacks (TIAs), and 2 percent as other (2). Stroke cases can also be classified by whether the vascular disease is extracerebral, intercranial, or intracerebral.