Declining mortality from stroke in Allegheny County, Pennsylvania. Trends in case fatality and severity of disease, 1971-1980.

Mortality rates for stroke in 1971, 1974, 1977, and 1980 were obtained for residents of Allegheny County in western Pennsylvania. Hospital case fatality ratios were also obtained in the same 4 years for those discharged with the diagnosis of stroke (ICD 430-438 of the Eighth and Ninth Revisions of the International Classification of Disease) in two large hospitals (greater than 400 beds). Age-adjusted mortality rates per 100,000 population have declined significantly in this period for the whole county as well as for the four sex-race groups. Case fatality ratio in the two hospitals of the study has decreased from 19.6 to 11%. A change in the severity of the disease manifested by a reduction in the number of comatose patients has occurred, and this reduction in comatose patients was responsible for greater than 80% of the decline in case fatality ratio. Coma appears to be the best predictor of mortality among hospitalized stroke cases (r = 0.6, p less than 0.00001). The recent introduction of computed tomography for the diagnosis of stroke in the late 1970s was accompanied by a twofold increase in the survivorship of stroke patients. However, this increase in survivorship may reflect selection bias and is based on ecological association. Further studies are needed to examine the role of computed tomography in improving survival.