Waist-to-height ratio centiles by age and sex for Japanese children based on the 1978-1981 cross-sectional national survey data

OBJECTIVES: To construct waist-to-height ratio (WC/Ht) reference values and centile curves for Japanese children and to compare these references with those from other countries. METHODS: The 1978-1981 national survey data were used for reference and the 1992-1994 national survey data were used for validation. The former included 19 233 children, and the latter included 10 446 children, aged 6 to 18 years. Waist circumferences (WC) were measured at the level of maximum waist narrowing in girls, and at the level of the top of the iliac crest in boys. Age-and sex-specific reference curves were fitted with the LMS method. Cut-off points were arbitrarily set at 85th, 90th, 95th and 97th centiles, and compared with WC/Ht 0.50. RESULTS: The proportion of children in whom WC/Ht exceeded 0.50 was 18.7% of boys and 1.9% of girls, whereas the proportion of children exceeding 90th centile was 42.4% for boys and 17.3% for girls. The reference values decreased with age in girls but varied by age without a clear trend in boys. CONCLUSIONS: The first reference values for WC/Ht are provided for Japanese youth based on the 1978-1981 national survey data. These curves are age-and sex-dependent, precluding the use of universal cut-off for WC/Ht of 0.50.