Fluid Intake and Blood Pressure in Children. The Spa Project

Background: Sodium intake is known to contribute to the development of hypertension. The reduction of sodium intake is currently a cornerstone in the prevention and management of hypertension. Inducing an increase in renal sodium excretion might represent a further potential preventive and/or therapeutic opportunity .Methods: The SPA Project is a multicenter, observational, cohort study aimed at investigating blood pressure in relation to fluid and sodium intake with the working hypothesis that an increased fluid intake can improve renal sodium handling towards a decreased blood pressure. Children were investigated as to their sodium and fluid intake by means of urinary sodium and creatinine from 4 samples of urine taken in different days in order to characterize them in low/high sodium and low/high fluid intake groups. Both systolic and diastolic blood pressure (by multiple office blood pressure measurements) were used as outcome measures.Findings: Three hundred and thirty-nine healthy, non-overweight children (51.6% boys) with a median age of 5.7 years old (IQR: 5.3-6.2) participated in the study. Among children with higher sodium intake, those introducing more fluids, showed a significantly lower blood pressure (both systolic and diastolic) compared to those with lower fluid intake: systolic 86.0 + 8.5 vs 90.0 + 8.1 mmHg; p: 0.014 and diastolic: 53.8 + 4.9 vs 58.6 + 6.6 mmHg; p<0.0001. A difference in blood pressure was not observed among children with lower sodium intake. Interpretation: Our findings support the hypothesis that an increased fluid intake reduces blood pressure possibly by increasing renal sodium excretion. We speculate that this simple, highly acceptable, inexpensive and harmless measure might have a role in preventing and/or minimizing the epidemics of hypertension and of its related morbidities both in children and in adults. Funding: The SPA Project was financed by an unrestricted research grant from private source. The funder did not participate in the work. Declaration of Interest: None to declare. Ethical Approval: Ethical approval was granted by the local ethical committee., The study was performed in accordance with the ethical standards of the Declaration of Helsinki and its later amendments.