Metabolic Syndrome in Chinese Children

Overweight was defined as a BMI ≥85th percentile and <95th percentile for gender and age, and obesity was defined as a BMI greater than or equal to the gender- and age-specific 95th percentile according to the Chinese BMI classification for children [25 ]. No universally-accepted threshold defines hyperuricemia in children; in this study, we defined hyperuricemia using the threshold of a UA value ≥357 μmol/L in accordance with previous studies [26 (link)]. Anaemia was defined according to the WHO criteria as a Hb <115 g/L for children aged ≥5 and <12 years, <120 g/L for children aged ≥12 and <15 years, <120 g/L for girls aged ≥15 years, and <130 g/L for boys aged ≥15 years [27 ]. Insulin resistance (IR) is affected by age and pubertal status [28 (link)], but no Tanner stage data was available for all participants in the database. To assess the age-related associations of MetS and IR, all children were divided into three age groups (7–10, 11–13, and 14–18 for girls; 7–11, 12–14, and 15–18 for boys) to reflect the prepubertal, pubertal, and postpubertal stages, respectively, according to the Chinese classification [29 (link),30 (link),31 (link)]. Currently, no universal definition of IR is applicable in normal and overweight children, so we adopted the 75th percentile of the homeostasis model assessment (HOMA: fasting serum insulin (μU/mL) × fasting plasma glucose (mmol/L)/22.5) within each age group as the threshold of IR [5 (link),32 (link)]. The IR thresholds assessed by the HOMA index are listed in Table 1.
In this study, MetS and its components in children aged 7–18 years were defined according to the modified criteria of the NCEP-ATP III [6 (link)]. MetS was identified when three or more of the following five components were present: (1) abdominal obesity: a WC equal to or above the gender- and age-specific 90th percentile for Chinese children [33 (link)]; (2) elevated TG: a TG ≥110 mg/dL; (3) low HDL: a HDL ≤40 mg/dL; (4) elevated blood pressure: an SBP and/or a DBP ≥90th percentile for gender, age, and height [24 (link)]; (5) elevated fasting glucose: a glucose ≥110 mg/dL. Moreover, the IDF definition was also applied to explore the concordance with the NCEP-ATP III definition in children aged 10–18 years [8 (link)].