Blood samples were obtained after at least an 8-hour overnight fast. The venous blood sample was then delivered to the central laboratory. Levels of fasting blood glucose, triglycerides, total cholesterol, and high-density lipoprotein cholesterol (HDL-C) were measured using an ADVIA 1650 chemistry analyzer (Siemens, Washington, DC, USA) in 2007, and a Hitachi 7600 automatic analyzer (Hitachi, Tokyo, Japan) from 2008 to 2010. For HDL-C, corrected values using the conversion equations recommended by the KCDC were used [22 (link)]. LDL-C was calculated using the Friedewald equation. Serum insulin was measured by 1470 Wizard gamma counter (Perkin-Elmer, Turku, Finland).
For quantification of IR, HOMA-IR was calculated as follows: HOMA-IR = fasting insulin (μU/dL) × fasting glucose (mg/dL) / 22.5. TyG index, TyG-WC, TyG-BMI were calculated using the formula published previously. The TyG index [17 (link),18 (link)]: Ln[TG (mg/ dL) × fasting glucose (mg/dL)/2]. TyG-BMI, TyG-WC and TyG-WHtR indicate TyG index x BMI [20 (link)], TyG index x WC [20 (link)] and TyG index x WHtR, respectively.
For quantification of IR, HOMA-IR was calculated as follows: HOMA-IR = fasting insulin (μU/dL) × fasting glucose (mg/dL) / 22.5. TyG index, TyG-WC, TyG-BMI were calculated using the formula published previously. The TyG index [17 (link),18 (link)]: Ln[TG (mg/ dL) × fasting glucose (mg/dL)/2]. TyG-BMI, TyG-WC and TyG-WHtR indicate TyG index x BMI [20 (link)], TyG index x WC [20 (link)] and TyG index x WHtR, respectively.