Low-Birth-Weight Babies at Risk for Salt Sensitivity

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MONDAY, Aug. 11 (HealthDay News) -- A Swiss study of 50 children found that almost half of those who were small at birth -- about 5.5 pounds or less -- had a significant increase in blood pressure when they ate a high-salt diet, a condition known as salt sensitivity.

"Salt sensitivity in children is low and rises with increasing age through adulthood," study author Dr. Giocomo D. Simonetti, a fellow in the division of pediatric nephrology at the Children's Hospital, University of Bern, said in an American Heart Association news release. The finding suggests that restricting salt intake in these children could improve their blood pressure.

"During adolescence, about 18 percent to 20 percent of adolescents in the general population have the condition. However, in the study, salt sensitivity was present in 37 percent of all low-birth-weight [LBW] and in 47 percent of the children ... who were small-for-gestational-age [SGA]."

The children in the study, average age of 11, included 15 who had normal birth weights and 35 who were LBW or SGA babies. Some were born prematurely and others were born at full term but were small due to growth restriction inside the womb. Causes of intrauterine growth restriction include maternal high blood pressure and maternal smoking during pregnancy.

During the study, the children ate a controlled sodium diet for a week and then a high-sodium diet for a week. The finding that children who were small at birth are more likely develop salt sensitivity is important, because high blood pressure can damage the kidneys, brain and heart.

"These children should be followed for signs of reduced renal function and also for an elevated blood pressure," study co-author Dr. Markus Mohaupt, head of the division of hypertension, department of nephrology/hypertension, University of Bern, said in the AHA news release.

"There's nearly a 50 percent chance of favorably affecting blood pressure by simply reducing salt intake in children born SGA and nearly a 40 percent chance for those born with LBW. These individuals can be determined very easily if their family physician just gets data on their births," Mohaupt said.

Among the other important study findings:

  • Salt sensitivity was inversely correlated to kidney size -- that is, smaller kidney size was associated with higher blood pressure. However, there was no association between kidney size and the organ's filtering abilities.
  • Kidneys in LBW children tended to be shorter and hold smaller volume compared to kidneys in normal birth weight children.
  • LBW children tend to be shorter than children of normal birth weight.

The study was published in the current issue of Hypertension.

More information

The Nemours Foundation has more about children and high blood pressure.

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