DALLAS, Oct. 21 -- A low blood cholesterol level in a teenager doesn't always indicate a "clean bill of health," according to a new study in today's issue of Circulation, an American Heart Association journal.
The study shows that surging hormones during puberty can lower cholesterol levels.
"The finding has important implications for assessing cholesterol levels in children," says Peter O. Kwiterovich Jr., M.D., a professor of pediatrics and chief of the lipid research- atherosclerosis division at Johns Hopkins University in Baltimore.
High cholesterol levels in the blood are considered one of the strongest predictors of a person's risk of heart disease. Children from families with heart disease are often tested for cholesterol to identify those who need to take steps to prevent heart disease.
"If a child comes from a family that has a high-risk for heart disease and has a cholesterol screen at age 13, a falsely low value will likely result. Those children will definitely have to be screened again after reaching young adulthood," says Kwiterovich.
The Dietary Intervention Study in Children study found that sexual maturation had the most powerful influence on cholesterol in boys and girls, having a greater effect than a low-fat diet.
The study included 663 girls and boys, ages 8 to 10, all with high cholesterol. Half the children (and their parents) attended a series of educational programs that focused on issues related to diet, including dietary saturated fat and cholesterol. Parents of the remaining children received "usual care," which included printed materials and notification of the children's high cholesterol levels.
Over the next three years, boys and girls in the special intervention group had significant declines in low-density lipoprotein (LDL) cholesterol, the "bad" cholesterol that leads to blockages in the blood vessels. However, LDL also declined in the usual care group, so that the overall difference between the groups was not as great as expected, reports Kwiterovich.
The researchers found that the degree of sexual maturation, defined by pubic hair development in boys and girls and breast development in girls, was associated with a notable decline in LDL.
But in face of the hormonal change of puberty the study also confirmed what other studies have shown: American children are getting heavier and have higher LDL levels. "Children are not eating more, as reflected by calories," he says. The weight gain could be due to decreased levels of physical activity, he adds.