The geographic variation in stroke incidence in two areas of the Southeastern Stroke Belt - The Anderson and Pee Dee Stroke Study

Background and Purpose-South Carolina and the southeastern United States have maintained the highest stroke mortality in the country. The Anderson and Pee Dee Stroke Study is an assessment of cerebrovascular disease incidence in 2 geographically defined communities in the stroke belt. Methods-Strokes were identified in the Anderson and Pee Dee areas of South Carolina. All hospitalized and out-of-hospital deaths occurring during 1990 among the residents of these 2 areas were included. Strokes were classified by an independent panel of neurologists using a standard protocol that included specific criteria for stroke and subtypes. Results-The overall age-adjusted stroke incidence rates (per 100 000 population) were significantly higher in the Pee Dee population (293.1) compared with Anderson (211.2). The geographic differences were more dramatic in the younger age groups of 35 to 64 years. Likewise, incidence rates for blacks were nearly twice the rates for whites. The rates in the Pee Dee were higher than the rates from other studies in the United States and other parts of the world. Although the stroke subtypes did not vary between the 2 regions, race-sex differences were identified. Conclusions-High stroke incidence and disease rates persist for all 4 race-sex groups in the Southeast and reflect similar risks as mortality rates, However, geographic variability in stroke rates suggests that the pattern of disease in the region is not so much a "belt" of increased stroke in contiguous areas but rather more a "necklace" of different levels of risk. These results should be useful in the identification of factors associated with this geographic enigma.