Metabolic syndrome in children and adolescents--risk for sleep-disordered breathing and obstructive sleep-apnoea syndrome?

The clinical relevance of the term "metabolic syndrome", the definition criteria, and predictive power are being disputed. Inclusion of sleep-disordered breathing and sleep apnoea into a definition of metabolic syndrome is also controversial once children and/or adolescents are affected. Nevertheless, along with the increasing prevalence of childhood obesity, the prevalence of the metabolic syndrome in obese children is reported at 30%, irrespective of the definition applied. Moreover, childhood obesity is associated with sleep-disordered breathing. Adipocytokines, cytokines secreted from adipose tissue, are thought to play a major role in the pathophysiology of metabolic syndrome. Leptin was initially suggested as a promising "anti-obesity" hormone. New concepts indicate that in humans leptin and its soluble receptor may be more important in states of energy deficiency rather than a predictor of the metabolic syndrome. Adiponectin, on the other hand, is not only related to obesity and insulin resistance, but appears to be the strongest predictor for metabolic syndrome, even in children. In newborns and infants, both adipocytokines occur in high concentrations, even though this cannot completely explain the increased risk for ensuing metabolic disease later in life. Finally, low-grade systemic inflammation may underlie the clustering of metabolic risk factors. Overall factors from the adipose tissue may constitute not only markers but also mediators of metabolic sequelae of obesity.