EBM Tools for Practice: Pediatric Metabolic Syndrome: Difficult to Define, Important to Treat

Although there is debate over the definition of metabolic syndrome in adults, the picture is even more clouded in pediatrics. Metabolic syndrome in adults is defined as having at least three of the following five cardiometabolic risk factors: hyperglycemia, increased central adiposity, elevated triglycerides, decreased HDL cholesterol and elevated blood pressure.(1) In pediatrics, there have been up to 40 definitions of metabolic syndrome proposed. The most commonly used definitions are quite similar to the adult definition; the primary difference is that only two criteria are needed (see Table 1).(2,3) Typically, metabolic syndrome in children is not formally diagnosed until the age of 10, but many children have risk factors which can and should be addressed prior to a formal diagnosis.(2)

Table 1. Diagnostic criteria for adult and pediatric metabolic syndrome. Pediatric criteria established for ages 10-16.
Adolescents over age of 16 are diagnosed based on adult criteria.
The most common lab abnormalities in children ages 10-16 were elevated triglycerides and low HDL-C.(1,3,5,18) WC = waist circumference, BP = blood pressure, T2DM = Type 2 Diabetes Mellitus

The prevalence of pediatric metabolic syndrome is about 4%, but this is heavily dependent on the definition used. Not surprisingly, the prevalence is higher in overweight and obese children (33%). In pediatrics, obesity is defined as a BMI greater than the 95th percentile based on age and gender. Approximately 1% of children with normal weight have metabolic syndrome, but up to 1/3 of normal weight children will have at least one of the components of metabolic syndrome.(4) Mexican American teens have the highest rate of metabolic syndrome at 5.6%, followed by African Africans and those of European ancestry at 4.8% and 2%, respectively.(5) Although the rate of metabolic syndrome has remained stable over recent years, obesity continues to trend upward, placing many children at risk.(4,6,7) Other risk factors for the development of pediatric metabolic syndrome are shown in Table 2.(3)

Rather than debating the exact definition of pediatric metabolic syndrome, some organizations have proposed that the focus should be on identifying and treating specific cardiometabolic risk factors. Regardless of the definition, the constellation of findings known as metabolic syndrome has significant implications for lifelong health including: increased risk of heart attack and stroke in adulthood as well as polycystic ovarian syndrome, obstructive sleep apnea, and type II diabetes.(3) Studies show that pediatric metabolic syndrome increases the risk of adulthood metabolic syndrome by 6 fold (Odds Ratio 6.2 [CI 2.8-13.8, p<0.001]) and cardiovascular disease in adulthood almost 15 fold (OR 14.6 [CI 4.8-45.3, P<0.0001]).(8) Regardless of the diagnosis, cluster tracking studies revealed that cardiovascular risk factors in childhood persist into adulthood in 25-60% of cases.(5)

What makes pediatric metabolic syndrome different from adult metabolic syndrome has been explored. Childhood is a period of rapid growth with physiologic fluctuations in lipid levels and insulin resistance. Many children defined as having metabolic syndrome do not meet diagnostic criteria 3-6 years later, although their metabolic risk factors remain consistent.(9) One study found that the diagnosis of metabolic syndrome was unstable in up to 1/3 of pediatric cases.(10) Due to this constant flux, the terms “metabolically healthy” or “metabolically unhealthy” in the obese pediatric population rather than “metabolic syndrome” are occasionally used. Unfortunately, “metabolically healthy” status in a prepubertal child does not guarantee a healthy child during or after puberty. Puberty is a period of natural insulin resistance and increases a child’s risk of developing metabolically syndrome, independently of a child’s BMI.(9,11-14) Alternatively, some children with risk factors during puberty may have normal findings at the end of puberty without intervention.(11,12) Obesity has been found to be a more stable trait throughout childhood, although waist circumference greater than or equal to the 90th percentile for age and gender better predicted cardiometabolic risk than BMI percentile alone.(15) Obesity does not guarantee the presence of cardiovascular risk factors, but it should prompt further investigation.

Ultimately, efforts should focus on identifying non-modifiable cardiometabolic risk factors, including birth history and family history, and treating lifestyle factors such as diet, physical activity, and sleep habits.(3, 16) Despite the disagreement on definition, it is well established that prevention and treatment of obesity is the first line approach to minimizing a child’s risk.(12) Lifestyle interventions of diet and exercise modification have been shown to produce significant improvements in obesity, LDL cholesterol, triglycerides, fasting insulin and blood pressure. Some studies have shown that this can be maintained, but data are mixed.(14) In pediatrics, involvement of the entire family is critical for success, and establishing regular family meal times, limiting “screen time” and  group physical activity are key interventions for lasting lifestyle modifications.(14,17)

Disclosure statement: Dr. Marten has no financial disclosures to report. Dr. Peterson has no financial disclosures to report.

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