Impact of nativity and race on "Stroke Belt" mortality.

The southeastern region of the United States has been recognized for 6 decades as an area of excess cerebrovascular mortality rates. While the reasons for the disease variation remain an enigma, South Carolina has consistently been the forerunner of the "Stroke Belt." To determine the effects of nativity (birthplace) on stroke mortality rates in South Carolina, proportional mortality ratios (PMRs) were calculated for stroke deaths in South Carolina during 1980-1996 according to birthplace and stratified by gender, race, age, and educational status. The analyses revealed a graded risk of stroke by birthplace, with the highest PMRs (95% CI) among individuals born in South Carolina (104.8 [103.4 to 106.3]), intermediate PMRs in those born in the Southeast other than South Carolina (92.5 [90.2 to 94.9]), and lowest PMRs for those born outside the Southeast (77.4 [74.9 to 80.1]). The lower stroke PMRs for individuals born outside the Southeast were more striking in blacks (51.8 [45.2 to 59.3]) than in whites (84.9 [82.0 to 88.0]) and for men (73.3 [69.5 to 77.3]) than women (83.5 [79.9 to 87.3]). The findings, particularly in blacks, were not explainable by gender, differences in age, and/or markers of educational and socioeconomic status. These findings suggest that nativity is a significant risk marker for the geographic variation in stroke mortality. Moreover, the regional disparities for nativity and subsequent stroke mortality appear to be greater in blacks than in whites and for men than for women. An understanding of factors linking birthplace to risk for cerebrovascular mortality could facilitate efforts directed at stroke prevention.