This article is more than 5 years old. Information may no longer be current.
Diagnosis of metabolic syndrome unstable in adolescents
Metabolic risk factor clustering is consistent despite diagnosis instability.
Click Here to Manage Email Alerts
Results from a study of more than 1,000 adolescents indicate that the diagnosis of metabolic syndrome is unstable in this population even though risk factor clustering remains consistent. The results call into question the clinical utility of a metabolic syndrome diagnosis in children and adolescents.
“At present, no consensus exists on the definition of pediatric metabolic syndrome,” the researchers wrote in Circulation. “The difficulties in creating a pediatric metabolic syndrome definition highlight the differences between metabolic syndrome as a concept and metabolic syndrome as a diagnostic category. The concept is based on clustering along an entire physiological spectrum, whereas the diagnostic category is based on dichotomies.”
Elizabeth Goodman, MD, director of the Child and Adolescent Obesity Program at Tufts-New England Medical Center and the Floating Hospital for Children in Boston, and colleagues conducted a study of 1,098 participants in the Princeton School District Study. During an average follow-up period of 2.74 years the researchers analyzed the stability of risk factors and the diagnosis of metabolic syndrome based on the American Heart Association and International Diabetes Federation definitions as well as a pediatric definition based on the AHA adult definition (pediatric AHA).
Baseline characteristics
The study cohort was 51.6% non-Hispanic white, 46.9% non-Hispanic black and 1.5% Hispanic; 50.5% of the participants were girls. The mean age at baseline was 15.0 years (range, 12.2 to 19.2 years). The baseline prevalence of overweight was 19.8% and obesity was 19.7%; at follow-up, these prevalences were 20.1% for overweight and 20.4% for obesity.
At follow-up, a total of 14.3% of individuals who were normal-weight at baseline were obese; 21.4% of those with a BMI in the 85th percentile or above at baseline were obese; and 77.9% of those who were obese at baseline were obese at follow-up.
To test the stability of risk-factor clustering, the investigators performed exploratory factor analysis, which extracted three factors at both baseline and follow-up: an adiposity factor consisting of insulin, BMI and waist circumference; a metabolic factor consisting of triglycerides and HDL cholesterol; and a blood pressure factor consisting of systolic and diastolic BP.
“Factor loadings and the amount of variance explained were similar at both time points,” they wrote. “The major difference was that glucose loaded on the metabolic factor at baseline and on the adiposity factor at follow-up. Also of note was that insulin loaded on the metabolic factor and the adiposity factor at baseline but only on the adiposity factor at follow-up.” They said that overall the differences were minor, suggesting a stable factor structure.
At baseline, 37 adolescents (3.4%) fulfilled the AHA definition for metabolic syndrome, whereas 57 (5.2%) fulfilled the pediatric AHA definition and 49 (4.5%) fit the IDF definition. At follow-up, these numbers had increased to 66 (6%) for the AHA definition, 65 (5.9%) for the pediatric AHA definition and 78 (7.1%) for the IDF definition.
“The number of new cases was greater than would have been expected from the prevalence data because the diagnosis was unstable in about half of those who were metabolic syndrome-positive at baseline,” the investigators wrote. The three definitions had instabilities of 48.6% (95% CI, 31.9-65.6) for the AHA definition, 56.1% (95% CI, 42.4-69.3) for the pediatric AHA definition and 53.1% (95% CI, 38.3-67.5) for the IDF definition.
Variation between metabolic syndrome groups
Between the three groups with metabolic syndrome (at baseline only, at follow-up only and persistent between both points), there were significant differences with regard to HDL cholesterol, triglycerides, systolic BP, waist circumference, BMI, height and weight. Insulin levels, glucose and diastolic BP were not significantly different.
“We need to take a giant step back from the idea that metabolic syndrome is clinically useful in pediatrics,” Goodman told Endocrine Today. “The data suggest that we cannot boil down this complex clustering of risks that hang together on a population level into a single yes or no clinical entity and apply it to specific individual children.”
Goodman also said that the factor analysis showing the stability of clustering along with the variation in risk factors used to define metabolic syndrome that is a normal part of pubertal growth and development implies that this is not a matter of simply adjusting the definition but a more fundamental conceptual problem.
This apparent instability in metabolic syndrome diagnosis in this population should call into question the idea that this is a clinical entity, which could be treated. “These data should inject a note of caution into the debate on pharmacotherapy for metabolic syndrome in kids,” Goodman said. – by Dave Levitan
For more information:
- Goodman E, Daniels SR, Meigs JB, et al. Instability in the diagnosis of metabolic syndrome in adolescents. Circulation. 2007;115:2316-2322.