Sodium, potassium and blood pressure in Australian schoolchildren: exploring differences by sex and weight status-a cross-sectional study.

Dietary sodium and potassium intake play a key role in the regulation of blood pressure (BP). This study investigated whether 24- urinary sodium, potassium and sodium-to-potassium ratio were associated with blood pressure in Australian schoolchildren aged 4-12 years, and if the association between 24-h urinary sodium and blood pressure was moderated by body weight. Twenty-four-hour urine, blood pressure, and anthropometry were collected from 755 schoolchildren (mean age 9.3 (SD 1.8) years). Multiple linear regression with adjustment for covariates was conducted. The mean sodium excretion was 2419 (SD 1052) mg/d. Seventeen percent of children had elevated blood pressure. There were no overall associations between 24-h sodium or potassium excretion and blood pressure in adjusted regression models. However, in adjusted regression analysis stratified by sex, there was a positive association between 24-h urinary sodium and systolic blood pressure z-score among girls (b-coefficient 0.10 95% CI 0.03, 0.18, pvalue = 0.01, n = 342). No other sex differences were observed. Body weight significantly moderated the association between sodium excretion and SBP (p for interaction = 0.002). In children living with obesity, sodium excretion was positively associated with systolic blood pressure z-score (b-coefficient 0.75 95% CI 0.00, 1.51, pvalue = 0.05, n = 21). In conclusion, sodium excretion in this sample exceeded recommended levels for healthy development and almost a fifth of children had elevated blood pressure. For optimal health across life, public health interventions aiming to reduce the elevated cardiovascular risk of raised blood pressure in children are likely to be most effective by reducing sodium intake in conjunction with promoting healthy weight.