Waist circumference and waist-to-height ratio in Norwegian children 4-18 years of age: Reference values and cut-off levels

Aim: To establish reference values for waist circumference and waist-to-height ratio of Norwegian children. Material: Data were collected in 2003-2006 as part of a cross-sectional study, including 5725 children 4-18 years of age. Reference curves were fitted with the LMS method; appropriate cut-offs were selected using receiver operating characteristic analysis. Results: Reference values for waist circumference and waist-to-height ratio are presented. Mean waist circumference increased with age for both genders. Boys had a higher waist circumference at almost all ages. Mean waist-to-height ratio decreased until early adolescence and thereafter increased slightly towards adult age. There was a strong positive correlation between waist circumference and BMI (r = 0.907, p < 0.01) and a moderate positive correlation between waist-to-height ratio and BMI (r = 0.397 p < 0.01). A waist circumference cut-off value of 1.0 SDS (85th percentile) gave a sensitivity of 79% and a specificity of 94% to detect overweight. A cut-off value of 1.6 SDS (95th percentile) gave a sensitivity of 94% and a specificity of 96% to detect obesity. Conclusion: This study presents the first reference values of waist circumference and waist-to-height ratio for Norwegian children 4-18 years, which also represent the first reference in Scandinavian schoolchildren. The 85th and 95th percentiles of waist circumference are proposed as appropriate cut-offs for central overweight and obesity.