In adults, the aggregation of multiple cardiovascular risk factors has been observed since the early part of the twentieth century. This clustering of risk factors has been called several things through the years, including syndrome X, insulin-resistant syndrome, and most recently, the metabolic syndrome. The metabolic syndrome is a cluster of a variable number of risk factors that exceed criterion values. These risk factors include an increased waist circumference (central adiposity), systemic hypertension, elevated fasting plasma triglyceride, and an elevated fasting glucose or insulin resistance. All of the components mentioned above have been identified in children, but they have not been universally described as the metabolic syndrome when these risk factors coexist.
Clinicians do not commonly recognizing that these components may coexist together in children and lead to future atherosclerotic cardiovascular disease in young adults. This is somewhat amazing because all of these precursors have been well described in children. The Bogalusa Heart Study showed that asymptomatic coronary and/or aortic atherosclerosis was directly related to the number of cardiovascular risk factors clustered under the metabolic syndrome. However, there is still no universally accepted definition for the metabolic syndrome in children.
In this issue of The Journal, we have collected nine articles which emphasize the fact that these various components need to be recognized and their interrelationships further defined and studied. A Commentary by Huang summarizes the work to date of the Pediatric Metabolic Syndrome Working Group (PMSWG) that has been convened to examine these risk factors and develop a standard frame for comparison across research studies. Ford et al and Cook et al review the numerous existing definitions for the metabolic syndrome in children and demonstrate that, depending upon the definition used, the incidence of metabolic syndrome varies widely. These two articles provide a compelling argument for the development of a single definition that can then be used to study the impact of this syndrome more carefully. Shaibi et al and Lee et al examine the possibility of using various predictive values for risk factors in children in order to develop cutoff values that will be of practical use as children grow older. In a similar fashion, Huang et al, Sun et al, and Morrison et al examine the results of tracking risk factors for metabolic syndrome in children as they become adults. Collectively, these are very important studies because they demonstrate that not only are all the components of the metabolic syndrome present in childhood, but they do, to some extent, predict the likelihood that these children will grow into adults with the metabolic syndrome.
Several deficiencies remain, however. The most glaring observation is that central adiposity is perhaps a more accurate predictor of metabolic syndrome and insulin resistance than body mass index (BMI). This suggests that clinicians soon will need to begin to collect and report waist circumference data (WC) or waist to height ratios (W/Ht) on their patients. The article by Maffeis et al confirms that WC and W/Ht are helpful in detecting children who are more likely to have the risk factors for the metabolic syndrome. In the future, these measurements may become more predictive and useful than BMI. Reference values that are sensitive to race, sex, and age will need to be created.
The obesity epidemic in children is out of control. Our children are living in an obesiogenic environment that fosters all of the components of the metabolic syndrome, regardless of the definition used. It is very likely that a high proportion of youth today who have all the components of the metabolic syndrome will go on to develop cardiovascular disease and type 2 diabetes in adulthood. Clinicians must continue to increase their awareness of the existence of the syndrome and begin to treat it before it becomes even more of a health hazard for our youth.
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