Neck circumference percentiles for obesity screening in Turkish children and adolescents: a cross-sectional study

This study aimed to establish neck circumference (NC) percentile values using the Lambda-Mu-Sigma (LMS) method among Turkish children and adolescents, to examine the relationship between NC and body mass index (BMI), and to identify optimal NC cut-off values for classifying IOTF-obesity and IOTF-overweight + obesity. This cross-sectional study included 4557 participants (2130 boys and 2427 girls) aged 6-18 years from Afyonkarahisar, Türkiye. Standard anthropometric measurements, including NC and BMI, were obtained. Age- and sex-specific smoothed NC percentile curves were generated using the LMS method. Age-adjusted partial correlation analysis was performed separately for boys and girls to examine the NC-BMI relationship. Receiver operating characteristic (ROC) curve analysis was performed to determine optimal NC cut-off values for classifying IOTF-obesity and IOTF-overweight + obesity. A strong positive correlation was observed between NC and BMI in boys (r = 0.69, 95% CI 0.66-0.72; p < 0.001) and girls (r = 0.64, 95% CI 0.61-0.67; p < 0.001). NC values increased with age and exhibited significant sexual dimorphism, particularly during puberty. Age-stratified NC cut-off values for identifying obesity (IOTF-obesity) and overweight/obesity (IOTF-overweight + obesity) were determined for three age groups (< 10, 10-14, and 15-18 years) in boys and girls. AUC values ranged from 0.78 to 0.93, indicating acceptable to excellent discriminatory ability.   Conclusion: This study provides age- and sex-specific NC reference values for Turkish children and adolescents. NC is a practical, reliable, and noninvasive anthropometric measure for obesity screening. The identified cut-off values might be useful in clinical and school-based settings for identifying children at risk of obesity. What is Known: • NC is a simple anthropometric measure associated with obesity and cardiometabolic risk in children and adolescents. • Population-specific percentile references are required because anthropometric indicators vary by ethnicity and region. What is New: • This study provides updated age- and sex-specific NC percentile reference values based on a large school-based sample from central Afyonkarahisar, Türkiye. • New NC cut-off values with acceptable to excellent discriminatory accuracy for obesity screening are proposed for clinical and school-based use.