The Renin-Angiotensin System, Capri 2005

Abstract

US Dietary Guidelines recommend sodium (Na) intake to be <2300 mg/day. The direct relationship of Na intake to blood pressure (BP) is established, but only a few inconsistent observational studies link Na with cardiovascular disease (CVD) outcomes. The Second National Health and Nutrition Examination Survey (NHANES II) and Mortality Study assessed dietary recall among 7154 subjects aged ≥30 years, free of heart disease, and not on low Na nor other special diets, nor who died within <6 months follow-up. Mean (± SE) age was 48 ± 0.3 years, mean weight 160 ± 0.4 pounds, 36% were smokers, 48% hypertensive. During a mean follow-up of 13.7 years (range 0.5-16.8) there were 584 CVD deaths. Hazard ratios (HR) and 95% CIs for Na and Na/calorie ratio (Na/KCal) were estimated with Cox regression models accounting for sampling and adjusting for CVD risk factors. Na as a continuous variable (per 1000mg) had a significant (p = 0.031) inverse association with CVD mortality (HR = 0.89, 95% CI: 0.81, 0.99), as did Na/KCal (HR = 0.80, 95% CI: 0.69, 0.94, p = 0.007). Dichotomising Na at <2300mg revealed significantly higher adjusted CVD risk (HR = 1.37, 95% CI: 1.03, 1.81, p = 0.033) associated with Na <2300mg. Results were consistent for all cause mortality (HR = 1.28, 95% CI: 1.1, 1.5, p = 0.003) and when stratified separately by weight, sex, smoking, or hypertensive status. The association of lower usual daily Na intake (as measured by a 24-hour dietary recall) with higher CVD mortality does not necessarily predict the consequences of change in Na intake. However, these robust data, reflecting experience of a large representative sample of the US population, indicating an inverse association of Na intake and cardiovascular mortality, do not support confidence that universal adherence to a dietary Na <2300mg will reduce CVD mortality or extend survival (figure 1, table I).