Background and purpose: Most Stroke Belt studies define exposure based on residence at stroke onset. We assessed whether residence in the Stroke Belt during childhood confers extra stroke risk in adulthood, even among people who left the region.
Methods: Stroke-free Health and Retirement Study participants (n=18 070) followed up (average, 8.4 years) for first stroke (1452 events) were classified as living in 1 of 7 Stroke Belt states in childhood or at study enrollment (average age, 63 years). We used Cox proportional-hazards models to compare stroke risk for people who had never lived in the Stroke Belt with those who had lived there at both ages, in childhood only, or in adulthood only.
Results: Compared with never having lived in the Stroke Belt, the hazard ratio for Stroke Belt residence in both childhood and adulthood was 1.23 (95% CI, 1.06, 1.43) and for Stroke Belt residence in childhood only was 1.25 (95% CI, 1.02, 1.55). Stroke Belt residence at enrollment but not during childhood was not significantly related to stroke risk (hazard ratio=1.01; 95% CI, 0.70, 1.46), but the small sample in this group resulted in wide CIs. Results changed little after risk factor adjustment, including comprehensive adult socioeconomic measures. Subgroup analyses found similar patterns by sex and birth cohort. In contrast, blacks who had lived in the Stroke Belt in childhood only did not appear to have significantly elevated stroke risk compared with blacks who had never lived in the Stroke Belt.
Conclusions: The excess stroke risk for people who had lived in Stroke Belt states during childhood implicates early life exposures in the etiology of the Stroke Belt.