Sleep-disordered breathing in adolescents with metabolic syndrome associated with increased sympathetic nervous system activity and leptin levels
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Sympathetic nervous system activity (SNSA) is elevated in subjects with sleep-disordered breathing, both in daytime and night time, especially during abnormal breathing bouts. The aim of this study was to investigate whether, in children presenting with metabolic syndrome and sleep-disordered breathing, metabolic markers separate them from children with metabolic syndrome but without sleep-disordered breathing. Subjects underwent overnight polysomnography, during which SNSA was estimated from the means of 8-hourly measurements of norepinephrine and epinephrine along with leptin. The morning thereafter, a fasting 3-hour oral glucose-tolerance test was carried out to calculate whole-body insulin sensitivity. Of the 34 children studied, 25 presented with sleep-disordered breathing. In children with sleep-disordered breathing, mean hourly norepinephrine and leptin levels were significantly higher than in those without sleep-disordered breathing, with no difference in whole-body insulin sensitivity. In the 11 subjects with sleep-disordered breathing who completed 3 months of nightly continuous positive airway pressure therapy, mean hourly leptin levels were significantly lower at the end of the 3-month treatment period compared to the initial study. These findings support the hypothesis that sleep-disordered breathing in children with metabolic syndrome is associated with increased SNSA and leptin levels but not with worsened insulin resistance. Moreover, a 3-month treatment with continuous positive airway pressure was associated with a significant decrease in leptin levels.
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