NEWS

By DAVID WILLIAMSON
UNC News Services

(Embargoed) CHAPEL HILL -- Pediatricians monitoring young patients’ health are more likely to recognize children as being overweight if they employ a measure known as body mass index than if they simply review the plot of each child’s height and weight, a new University of North Carolina at Chapel Hill study concludes.

Too few pediatricians, however, use the body mass index in their physicals and evaluations, researchers found. Almost a third never consider the index, also called BMI, which is a mathematically derived number indicating how heavy a person is for his or her height.

The research is the first to demonstrate the greater usefulness of children’s BMI charts over pediatricians’ traditional health and weight charts in identifying overweight children and in stimulating reports of health concerns, investigators say.

A paper about the findings appears in the April issue of the Journal of Pediatrics. Authors are Dr. Eliana Miller Perrin, Kori B. Flower and Alice S. Ammerman of UNC’s schools of medicine and public health, nutrition department and Center for Health Promotion and Disease Prevention.

"Childhood overweight constitutes a major health problem," said Perrin, assistant professor of general pediatrics and adolescent medicine.

"Based on the definition for childhood overweight recommended by the Centers for Disease Control and Prevention and an expert committee, the current prevalence of childhood overweight is between 10 percent and 15 percent in the United States and is continuing to escalate."

Despite their strong links to diabetes, high blood pressure and cardiovascular disease in later life, overweight and obesity frequently are under-diagnosed in both children and adults, the study noted.

"In our sample, only 11 percent of pediatricians always reported using BMI when they were deciding if someone was overweight," Perrin said. "This is useful information since improving recognition of an emerging weight problem may be an important first step in curbing this escalating epidemic."

In their study, she and her colleagues surveyed by mail North Carolina Pediatrics Society members who also were American Academy of Pediatrics members. Seventy-one percent of those queried responded and were divided into two groups.

The questionnaires provided either height and weight or body mass index information, along with other details, about the same hypothetical overweight 10-year-old child. Doctors were asked to rate how overweight the fictitious girl was and their own level of concern about her. Researchers also asked the doctors how often they used height and weight, body mass index or other diagnostic methods to screen for weight problems generally.

When asked to rate the girl in the vignette on a scale of 1 to 7 as being "too thin" to "too fat," respondents in the BMI group perceived the child as closer to the overweight extreme than did those receiving separate height and weight charts, Perrin said. Those looking at her BMI chart also indicated greater concern for the child’s current and future physical and psychological health than did those looking at her eight and weight charts.

How often doctors used BMI was not related to their ages, sex, ethnicity or the types of practices or communities they were in or patients they saw, according to the study.

Perrin became interested in the importance of body mass index when she noticed that pediatricians in her clinic tended to report children as being of normal weight even if their weight was much higher for their age than their height was. That’s because interpreting two numbers on two charts is harder than reviewing one number on one chart.

"We did this study because there are a lot of recommendations that pediatricians do something about the emerging epidemic of obesity, most recently from the American Academy of Pediatrics, which encouraged pediatricians to monitor children’s BMI yearly," she said. "Given this recommendation, we wanted to find out whether doctors would be more concerned about children’s weight if they used BMI than if they did not."

That so many pediatricians don’t use BMI despite its benefits means medical scientists need to figure out why, Perrin said.

"Lots of Web-based and Palm Pilot programs can make the calculation from height and weight to BMI simpler, but it’s still one extra step to take on a busy patient-filled day," she said. "We hope to find ways to make it easier for doctors to take this important step and convey the information clearly and sensitively to patients and parents."

BMI is calculated by taking one’s weight in kilograms and dividing that number by one’s height in meters squared. That number is then plotted on charts that give population norms for both boys and girls ages 2 to 20.

"Whereas adults should ideally have body mass indexes that are less than 25, for children appropriate BMI is age and gender-dependent," Perrin said. "That’s why it is useful to have BMI charts that help pediatricians see when a child is too heavy for his or her height."

Children are overweight when their BMI-for-age is greater than the 95th percentile, she said. They are at risk for overweight when their BMI is between the 85th and 95th percentiles.

- 30 -

Note: Perrin can be reached at (919) 966-2504 or eperrin@email.unc.edu
Media Contact: David Williamson, (919) 962-8596