Urinary sodium excretion, blood pressure, cardiovascular disease, and mortality: a community-level prospective epidemiological cohort study.

Abstract (PubMed)

BACKGROUND: WHO recommends that populations consume less than 2 g/day sodium as a preventive measure against cardiovascular disease, but this target has not been achieved in any country. This recommendation is primarily based on individual-level data from short-term trials of blood pressure (BP) without data relating low sodium intake to reduced cardiovascular events from randomised trials or observational studies. We investigated the associations between community-level mean sodium and potassium intake, cardiovascular disease, and mortality. METHODS: The Prospective Urban Rural Epidemiology study is ongoing in 21 countries. Here we report an analysis done in 18 countries with data on clinical outcomes. Eligible participants were adults aged 35-70 years without cardiovascular disease, sampled from the general population. We used morning fasting urine to estimate 24 h sodium and potassium excretion as a surrogate for intake. FINDINGS: 95,767 participants in 369 communities were assessed for BP and 82,544 in 255 communities for cardiovascular outcomes with follow-up for a median of 8.1 years. Mean systolic BP increased by 2.86 mm Hg per 1 g increase in mean sodium intake, but positive associations were only seen among communities in the highest tertile of sodium intake (p<0.0001 for heterogeneity). The association between mean sodium intake and major cardiovascular events showed significant deviations from linearity (p=0.043) due to a significant inverse association in the lowest tertile. All major cardiovascular outcomes decreased with increasing potassium intake. INTERPRETATION: Sodium intake was associated with cardiovascular disease and strokes only in communities where mean intake was greater than 5 g/day. A strategy of sodium reduction in these communities and countries but not in others might be appropriate.