An analysis of the link between strokes and soils in the South Carolina coastal plains

Abstract

The Stroke Belt is a geographical region of the Southeastern United States where resident individuals suffer a disproportionately higher rate of strokes than the rest of the population. While the “buckle” of this Stroke Belt coincides with the Southeastern Coastal Plain region of North and South Carolina and Georgia, there is a paucity of information pinpointing specific causes for this phenomenon. A number of studies posit that an exposure event–potentially microbial in nature–early in life, could be a risk factor. The most likely vector for such an exposure event would be the soils of the Southeastern Coastal Plain region. These soils may have chemical and physical properties which are conducive to the growth and survival of microorganisms which may predispose individuals to stroke. To this aim, we correlated SC stroke mortality data to soil characteristics found in the NRCS SSURGO database. In statewide comparisons, depth to water table (50 to 100 cm, R = 0.62) and soil drainage class (poorly drained, R = 0.59; well drained, R = −0.54) both showed statistically significant relationships with stroke rate. In a 20 county comparison, depth to water table, drainage class, hydric rating (hydric soils, R = 0.56), and pH (very strongly acid, R = 0.66) all showed statistically significant relationships with stroke rate. These data should help direct future research and epidemiology efforts to pinpoint the exact exposure events which predispose individuals to an increased stroke rate.

Keywords:

• Environmental exposure
• geostatistical analysis
• soil
• South Carolina
• SSURGO
• Stroke Belt
• stroke buckle

Acknowledgments

We would like to thank Dean Evans for assistance with the preparation of the data used in this manuscript, and Patricia Donovan for GIS advice and manuscript review. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.

Authors T.F.D. and J.O.M. contributed equally to the writing of this manuscript.