Background: Understanding how the timing of exposure to the US Stroke Belt (SB) influences stroke risk may illuminate mechanisms underlying the SB phenomenon and factors influencing population stroke rates. Methods: Stroke mortality rates for United States' born black and white people aged 30-80 years were calculated for 1980, 1990, and 2000 for strata defined by birth state, state of adult residence, race, sex, and birth year. Four SB exposure categories were defined: born in a SB state (North Carolina, South Carolina, Georgia, Tennessee, Arkansas, Mississippi, or Alabama) and lived in the SB at adulthood; non-SB born but SB adult residence; SB-born but adult residence outside the SB; and did not live in the SB at birth or in adulthood (reference group). We estimated age-, sex-, and race-adjusted odds ratios for stroke mortality associated with timing of SB exposure. Results: Elevated stroke mortality was associated with both SB birth and, independently, SB adult residence, with the highest risk among those who lived in the SB at birth and adulthood. Compared to those living outside the SB at birth and adulthood, odds ratios for SB residence at birth and adulthood for black subjects were 1.55 (95% confidence interval 1.28, 1.88) in 1980, 1.47 (1.31, 1.65) in 1990, and 1.34 (1.22, 1.48) in 2000. Comparable odds ratios for white subjects were 1.45 (95% confidence interval 1.33, 1.58), 1.29 (1.21, 1.37), and 1.34 (1.25, 1.44). Patterns were similar for every race, sex, and age subgroup examined. Conclusion: Stroke Belt birth and adult residence appear to make independent contributions to stroke mortality risk.
Dr. M. Maria Glymour, 677 Huntington Avenue, Kresge 617, Boston, MA 02115