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Association of urinary sodium excretion with blood pressure and cardiovascular clinical events in 17,033 Latin americans

Abstract:

BACKGROUND Information on actual sodium intake and its relationships with blood pressure (BP) and clinical events in South America is limited. The aim of this cohort study was to assess the relationship of sodium intake with BP, cardiovascular (CV) events, and mortality in South America. METHODS We studied 17,033 individuals, aged 35-70 years, from 4 South American countries (Argentina, Brazil, Chile, and Colombia). Measures of sodium excretion, estimated from morning fasting urine, were used as a surrogate for daily sodium intake. We measured BP and monitored the composite outcome of death and major CV events. RESULTS Overall mean sodium excretion was 4.70 ± 1.43 g/day. A positive, nonuniform association between sodium and BP was detected, with a significant steeper slope for the relationship at higher sodium excretion levels (P < 0.001 for interaction). With a median follow-up of 4.7 years, the primary composite outcome (all-cause death, myocardial infarction, stroke, or heart failure) occurred in 568 participants (3.4%). Compared with sodium excretion of 5-6 g/day (reference group), participants who excreted >7 g/day had increased risks of the primary outcome (odds ratio (OR) 1.73; 95% confidence interval (CI) 1.24 to 2.40; P < 0.001), as well as death from any cause (OR 1.87; 95% CI 1.23 to 2.83; P = 0.003) and major CV disease (OR 1.77; 95% CI 1.12 to 2.81; P = 0.014). Sodium excretion of <3 g/day was associated with a statistically nonsignificant increased risk of the primary outcome (OR 1.20; 95% CI 0.86 to 1.65; P = 0.26) and death from any cause (OR 1.25; 95% CI 0.81 to 1.93; P = 0.29), and a significant increased risk of major CV disease (OR 1.50; 95% CI 1.01 to 2.24; P = 0.048), as compared to the reference group. CONCLUSIONS Our results support a positive, nonuniform association between estimated urinary sodium excretion and BP, and a possible J-shaped pattern of association between sodium excretion over the entire range and clinical outcomes.