Neck circumference as a simple tool for identifying the metabolic syndrome and insulin resistance: results from the Brazilian Metabolic Syndrome Study

Summary Objective To investigate the relationship of the neck circumference ( NC ) with the metabolic syndrome ( M et S ) and insulin resistance ( IR ) in a large Brazilian population‐based sample, within a wide range of adiposity and glucose tolerance, and to establish cut‐off values of the NC for M et S and IR . Context The NC correlates with cardiovascular risk factors, IR and components of M et S . Upper‐body subcutaneous (sc) fat, as estimated by the NC , is associated with cardiovascular risk factors as much as abdominal fat, which is usually estimated by the waist circumference ( WC ). There are few epidemiological population‐based studies on the clinical significance of the NC to M et S and IR . Design This is a cross‐sectional study. Patients About 1053 Brazilian adults (18–60 years). Measurements Patients with BMI 18·5–40·0 kg/m 2 , with normal glucose tolerance or type 2 diabetes (T2 DM ), were submitted to anthropometric measurements including waist circumference ( WC ), NC and BMI . Abdominal visceral fat ( VF ) was assessed by ultrasound. Insulin sensitivity ( IS ) was assessed by euglycaemic–hyperinsulinaemic clamp (10% of total sample) and HOMA ‐ IR . Spearman correlations were used to evaluate the association between NC and IR and M et S risk factors. Receiver operating characteristic ( ROC ) curves were used for gender‐specific cut‐off values for the prediction of IR and M et S . Binary logistic regression analysis was used to assess the chance of developing IR or M et S according to the enlargement of NC and WC . Results The sample consisted of 28·6% men, with a mean age of 39·4 (12 years). T2 DM diagnosis was present in 306 individuals, of whom 34% were men. NC correlated with WC and BMI in both men and women ( P  < 0·001). In both genders, NC showed a positive correlation with triglycerides, fasting glucose, fasting insulin and HOMA ‐ IR , and NC had a negative association with high‐density lipoprotein ( HDL ). NC and IS showed a moderate negative correlation. A significant correlation was demonstrated between VF and NC . In the ROC curves, NC presented the largest AUC for IR in women ( P  < 0·001), while NC presented a large AUC for M et S in both genders. Conclusions Neck circumference measurements are an alternative and innovative approach for determining body fat distribution. The NC is positively associated with M et S risk factors, IR and VF , with established cut‐off values for the prediction of MetS and IR .