Patterns of incidence and trends in diagnostic classification of cerebrovascular disease in Washington County, Maryland, 1969-1971 to 1974-1976.

A study was conducted to provide baseline data on patterns of cerebrovascular disease incidence in the community of Washington County, Maryland, over two time intervals--1969-1971 and 1974-1976--and to evaluate any temporal trends with regard to their possible relation to reported declines in stroke death rates. Among the statistically significant changes in incidence between 1969-1971 and 1974-1976 were a decline in the rate of cerebral thrombosis and a concomitant increase in frequency of cerebrovascular disease-unspecified, most likely a reflection of a change in diagnostic terminology. In addition, the findings of a significant decrease in incidence of cerebral hemorrhage (for all ages over 55 years and both sexes) and a non-significant decrease in incidence rates for all types combined among those in the oldest age category between the two study periods support the role of changing incidence rates in the stroke death rate decline. It is clear, however, that monitoring of this community over a longer period of time will be necessary before the validity of these trends can be established and their causes elucidated. The need for more complete recording of historical data and clinical findings on admission, as well as adherence to standardized diagnostic and classification protocols was underscored by this study.