Introduction:
Evidence from randomized controlled trials demonstrates higher sodium and/or lower potassium intake increase blood pressure and the risk of hypertension. However, the relationship between sodium, potassium and blood pressure has not been examined using nationally representative sample and estimated usual intakes of these nutrients.
Hypothesis:
We hypothesized that usual sodium and potassium intake have opposing effects on blood pressure and a higher sodium-to-potassium ratio is associated with elevated blood pressure and hypertension.
Methods:
We analyzed data on 12,854 participants aged 20 years and older from the 2003-2008 National Health and Nutrition Examination Surveys. We estimated the usual intakes of sodium and potassium from the diet accounting for measurement error. Mean blood pressure was calculated from up to three readings on each subject and hypertension included both diagnosed and undiagnosed hypertension. We used multivariable linear regression to examine the associations between intakes of sodium, potassium and their ratio with systolic and diastolic blood pressure, and logistic regression for associations with hypertension.
Results:
The average estimated usual intakes of sodium and potassium were 3465 and 2741 mg/d, respectively. The average sodium-to-potassium ratio was 1.39; higher ratios were observed among males, younger and non-Hispanic black participants. After adjustment for potential confounders, usual intakes of sodium, potassium and their ratio were significantly associated with systolic blood pressure, with an increase of 1.08 mm Hg (95% confidence interval (CI): 0.30 – 1.86) and a decrease of 1.47 mmHg (95% CI: -2.31, -0.63) for every 1000 mg/d increase in sodium and potassium intake, respectively, and an increase of 2.80 mmHg (95% CI: 0.90 - 4.70) for every unit increase in sodium-to-potassium ratio. No association was found for diastolic blood pressure. The adjusted odds ratio (OR) comparing the highest and lowest quartiles of usual sodium or potassium intakes were 1.63 (95% CI: 1.14 - 2.34) and 0.61 (95% CI: 0.45 - 0.82), respectively, for risk of hypertension. For sodium-to-potassium ratio, the adjusted OR was 1.49 (95% CI: 1.17 - 1.89). The patterns of association were largely consistent across age, gender, race/ethnicity, body mass index, and education subgroups.
Conclusions:
In conclusion, our results indicated higher sodium and lower potassium intakes were associated with increased systolic blood pressure and risk for hypertension. The combined effect of sodium and potassium might play a central role in the pathogenesis of hypertension. The results further confirm that reducing sodium and increasing potassium intakes concurrently may have important implications in the prevention of hypertension, and hence, of cardiovascular disease.
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