Salt intake and stroke: a possible direct effect

We have performed an ecological analysis of the relationship between regional mortality from cerebrovascular disease in western Europe and regional data on urinary sodium excretion, systolic blood pressure and relevant confounding variables. We have used published WHO cerebrovascular disease mortality rates and data provided by the INTERSALT study. Inter-relationships between these variables were investigated by linear regression analysis, with the regression coefficients, weighted for population size. On univariate analysis a significant linear relationship was observed between regional stroke mortality and median 24 hour urinary sodium excretion (coef. = 0.01, t = 3.28, P = 0.008), body mass index (coef. = 0.24, t = 3.21, P = 0.009) and alcohol intake (mls/week, coef. = 1.54, t = 3.99, P = 0.003). The relationship between stroke mortality and systolic blood pressure, though positive, was weaker than that between stroke mortality and sodium excretion and was not significant in this data. The stroke mortality sodium excretion relationship was independent of BMI on multivariate analysis. These data are consistent with the hypothesis that a high intake of salt may increase the risk of stroke, independent of effects on blood pressure.