February 11, 2003 |
Boys born lean have an increased risk of elevated blood pressure in their teens if they add a lot of weight between ages 8 and 15, researchers report in today’s rapid access issue of Hypertension: Journal of the American Heart Association. “The boys who were thinnest at birth and who gained the most weight during childhood and adolescence were the ones who had the greatest risk of high blood pressure,” says lead author Linda S. Adair, Ph.D., professor of nutrition at the University of North Carolina at Chapel Hill Schools of Medicine and Public Health.
From the American heart Association:
Boys thin at birth but heavy as teens face risk for high blood pressure
DALLAS, Feb. 11 ? Boys born lean have an increased risk of elevated blood pressure in their teens if they add a lot of weight between ages 8 and 15, researchers report in today’s rapid access issue of Hypertension: Journal of the American Heart Association.
“The boys who were thinnest at birth and who gained the most weight during childhood and adolescence were the ones who had the greatest risk of high blood pressure,” says lead author Linda S. Adair, Ph.D., professor of nutrition at the University of North Carolina at Chapel Hill Schools of Medicine and Public Health.
In contrast, adolescents with more rapid growth in the first two years of life, as opposed to later in childhood, were not at increased risk of having elevated blood pressure in adolescence, regardless of whether they were thin at birth, she says.
“Faster growth in infancy did not represent a risk for increased blood pressure in adolescence for either sex,” Adair says. “This period of weight gain may even be slightly protective against high blood pressure later. This is an important finding because pediatricians want to see improved growth in babies born small.”
Intriguingly, the researchers did not find any relationship between body proportions at birth and the risk of elevated blood pressure in adolescence among the girls in the study.
“The sex difference is a big question that we cannot answer,” Adair says. “We thought the reason might be related to sexual maturity, but when we controlled for it in our analysis, it didn’t make a difference.”
Low birth weight in full-term infants may be evidence of growth retardation in the womb, Adair says. The new findings are consistent with the fetal programming or Barker hypothesis, named after its main advocate, David J. P. Barker, M.D., Ph.D., of the University of Southampton in England.
The hypothesis holds that a malnourished fetus will adapt its metabolism to survive in the womb until birth, but that these changes put a person at increased risk of several chronic diseases ? including cardiovascular ailments, diabetes and perhaps cancer ? later in life.
Adair and biostatistician Tim J. Cole, Sc.D., of the Institute of Child Health in London, tested the hypothesis by examining whether low birth weight was related to later elevated blood pressure.
They used data from the Cebu Longitudinal Health and Nutrition Survey, in which Adair has been involved since 1986. It continues to follow more than 2,000 persons born between 1983-84 in and near Cebu, the Philippines’ second largest city.
Most fetal programming studies lack data between birth and the measurement of the ailment being studied.
“The value of the Cebu study is that we have repeated measurements of these kids from birth,” Adair says. “We know about their growth, nutrition, infectious diseases and physical activity, all of which can affect risk factors.”
In their analysis, the two researchers took all the things that might increase blood pressure into account. The long-lasting effects of birth size remained important, even after accounting for other factors, thus lending more credence to the fetal programming hypothesis, says Adair.
“Using more detailed information from birth to adolescence allowed us to pinpoint the time periods when growth matters most. It turns out that growth during infancy, in this study at least, was not a risk factor, but more rapid weight gain later on was,” Adair says.
However, in adolescent boys, increased risk of high blood pressure associated with faster weight gain in childhood and adolescence was found only in those who were thin at birth.
For girls, large weight gains during ages 8 to 15 increased their risk of elevated blood pressure, but the risk was unrelated to birth weight.
The study results demonstrate the need for pregnant women to receive adequate nutrition and healthcare to avoid fetal growth retardation, Adair concludes.