Associations of sodium, potassium and protein intake with blood pressure and hypertension in Switzerland

Abstract

Background: Nutritional factors play an important role in the regulation of blood pressure and in the de-velopment of hypertension. In this analysis, we ex-plored the associations of 24-hour urinary Na+, K+ and urea excretion with blood pressure levels and the risk of hypertension in the Swiss population, taking regional linguistic differences into account. Methods: The Swiss Survey on Salt is a population based cross-sectional study that included 1336 subjects from the three main linguistic regions (French, German and Italian) of Switzerland. Blood pressure was meas-ured with a validated oscillometric Omron HEM 907 device. Hypertension was defined as current antihyper-tensive treatment or a mean systolic blood pressure >140 mm Hg and/or diastolic >90 mm Hg, based on eight blood pressure measurements performed at two visits. Na+, K+ and urea excretion were assessed in 24-hour urine collections. We use multiple logistic/linear regressions to explore the associations of urine Na+, K+ and urea with blood pressure / hypertension, taking into account potential confounders and effect modifiers. RESULTS: The prevalence of hypertension was 30%, 26% and 17% in the German-, French- and Italian- speaking regions respectively, (p-value across regions <0.001). In the Swiss adult population, besides age, sex, and body mass index, urinary Na+ excretion was posi-tively associated with systolic blood pressure and hy-pertension. Urinary K+ excretion tended to be negatively associated with blood pressure but this was not signifi-cant (p = 0.08). Hypertensive people had a higher 24-hour urinary Na+/K+ ratio than normotensive people (p = 0.003). Urinary urea excretion was associated with nei-ther blood pressure nor hypertension. Participants from the German-speaking region had a higher likelihood of having a high systolic blood pressure. CONCLUSIONS: We confirm a high prevalence of ele-vated blood pressure in Swiss adults, including regional differences. In Switzerland, urinary Na+ excretion is associated positively with blood pressure and hyperten-sion, independently of urinary K+ and urea excretion. The observed differences in blood pressure levels across linguistic regions are independent of the urinary Na+, K+ and urea excretion.