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(Hypertension. 2008;52:625.)
© 2008 American Heart Association, Inc.

Original Articles

Salt Sensitivity of Children With Low Birth Weight

Giacomo D. Simonetti; Luigi Raio; Daniel Surbek; Mathias Nelle; Felix J. Frey; Markus G. Mohaupt

From the Divisions of Pediatric Nephrology and Neonatology (M.N.), Children’s Hospital, and Departments of Nephrology and Hypertension (G.D.S., F.J.F., M.G.M.) and Obstetrics and Gynecology (L.R., D.S.), Inselspital, Bern University Hospital and University of Bern, Berne, Switzerland.

Correspondence to Markus G. Mohaupt, Division of Hypertension, Department of Nephrology and Hypertension, University of Bern, CH-3010 Berne, Switzerland. E-mail markus.mohaupt{at}insel.ch

Compromised intrauterine fetal growth leading to low birth weight (<2500 g) is associated with adulthood renal and cardiovascular disease. The aim of this study was to assess the effect of salt intake on blood pressure (salt sensitivity) in children with low birth weight. White children (n=50; mean age: 11.3±2.1 years) born with low (n=35) or normal (n=15) birth weight and being either small or appropriate for gestational age (n=25 in each group) were investigated. The glomerular filtration rate was calculated using the Schwartz formula, and renal size was measured by ultrasound. Salt sensitivity was assigned if mean 24-hour blood pressure increased by 3 mm Hg on a high-salt diet as compared with a controlled-salt diet. Baseline office blood pressure was higher and glomerular filtration rate lower in children born with low birth weight as compared with children born at term with appropriate weight (P<0.05). Salt sensitivity was present in 37% and 47% of all of the low birth weight and small for gestational age children, respectively, higher even than healthy young adults from the same region. Kidney length and volume (both P<0.0001) were reduced in low birth weight children. Salt sensitivity inversely correlated with kidney length (r²=0.31; P=0.005) but not with glomerular filtration rate. We conclude that a reduced renal mass in growth-restricted children poses a risk for a lower renal function and for increased salt sensitivity. Whether the changes in renal growth are causative or are the consequence of the same abnormal "fetal programming" awaits clarification.

Key Words: arterial hypertension • Barker’s hypothesis • Brenner’s hypothesis • low birth weight • salt sensitivity • small for gestational age