Sodium intake and mortality follow-up in the Third National Health and Nutrition Examination Survey (NHANES III)

BACKGROUND: Sodium restriction is commonly recommended as a measure to lower blood pressure and thus reduce cardiovascular disease (CVD) and all-cause mortality. However, some studies have observed higher mortality associated with lower sodium intake. OBJECTIVE: To test the hypothesis that lower sodium is associated with subsequent higher cardiovascular disease (CVD) and all cause mortality in the Third National Health and Nutrition Examination Survey (NHANES III). DESIGN: Observational cohort study of mortality subsequent to a baseline survey. PARTICIPANTS: Representative sample (n = 8,699) of non-institutionalized US adults age >= 30, without history of CVD events, recruited between 1988-1994. MEASUREMENTS AND MAIN RESULTS: Dietary sodium and calorie intakes estimated from a single baseline 24-h dietary recall. Vital status and cause of death were obtained from the National Death Index through the year 2000. Hazard ratio (HR) for CVD mortality of lowest to highest quartile of sodium, adjusted for calories and other CVD risk factors, in a Cox model, was 1.80 (95% CI 1.05, 3.08, p = 0.03). Non-significant trends of an inverse association of continuous sodium (per 1,000 mg) intake with CVD and all-cause mortality were observed with a 99% CI of 0.73, 1.06 (p = 0.07) and 0.86, 1.04 (p = 0.11), respectively, while trends for a direct association were not observed. CONCLUSION: Observed associations of lower sodium with higher mortality were modest and mostly not statistically significant. However, these findings also suggest that for the general US adult population, higher sodium is unlikely to be independently associated with higher CVD or all-cause mortality.