Aim: The aim of this study was to establish reference values for waist circumference among Japanese youths using the 1978-1981 nationally representative data. Subject and methods: Growth charts were derived using Cole's LMS method, which adjusts the waist circumference distribution for skewness and allows waist circumference to be expressed as centile or standard deviation score. The sample population consisted of 19 233 children aged 6-18 years. Waist circumference was measured at the level of maximum waist narrowing in girls and at the level of the top of the iliac crest in boys. Results: Comparison was made between the 1978-1981 and 1992-1994 waist circumference charts, showing a large increase in waist circumference over time; the mean difference was 1.1 and 0.5 SD score units in boys and girls, respectively. Defining cut-offs for central fatness as the 90th and 95th centiles of the 1978-1981 reference, the prevalences in 1992-1994 were, respectively, 42.3% and 25.2% in boys and 19.1% and 10.9% in girls. The corresponding prevalences in 1978-1981 were 10% and 5% by definition. Conclusion: This study showed increasing trends in waist circumference, particularly in boys during the period of the two surveys and that the 1978-1981 charts serve as better baseline references for waist circumference among Japanese youth.
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