Lower Levels of Sodium Intake and Reduced Cardiovascular Risk
Background—Recent studies have raised the possibility of adverse effects of low sodium, particularly less than 2300 mg/24hr, on cardiovascular disease (CVD). However, these paradoxical findings might have resulted from suboptimal measurement of sodium and potential biases related to indication or reverse causation.
Methods and Results—Phases I and II of the Trials of Hypertension Prevention (TOHP) collected multiple 24-hour urine specimens among pre-hypertensive individuals. During extended post-trial surveillance, 193 cardiovascular events or CVD deaths occurred among 2275 participants not in a sodium reduction intervention with 10 (TOHP II) or 15 (TOHP I) years of post-trial follow-up. Median sodium excretion was 3630 mg/24hr, with 1.4% of the participants having intake <1500 mg/24hr and 10% <2300 mg/24hr, consistent with national levels. Compared to those with sodium excretion of 3600 to <4800 mg/24hr, risk for those with sodium <2300 mg/24hr was 32% lower after multivariable adjustment (HR=0.68, 95%CI = 0.34-1.37, p for trend = 0.13). There was a linear 17% increase in risk per 1000 mg/24hr (p=0.05). Spline curves supported a linear association of sodium with cardiovascular events, continuing to descend from 3600 to 2300 and 1500 mg/24hr, although the data were sparse at the lowest levels. Controlling for creatinine levels had little effect on these results.
Conclusions—Results from the TOHP studies, which overcome the major methodological challenges of prior studies, are consistent with overall health benefits of reducing sodium intake to the 1500 to 2300 mg/day range in the majority of the population, in agreement with current dietary guidelines.
- Received August 30, 2013.
- Revision received November 22, 2013.
- Accepted December 2, 2013.