WHO 2006 Child Growth Standards overestimate short stature and underestimate overweight in Japanese children

It is unclear whether the World Health Organization (WHO) 2006 Child Growth Standards are applicable to East Asian populations. We investigated the applicability of the WHO standards of length/height and weight to a cohort representing middle-class children in Japan. A cohort of children aged 0-5 years (3430 boys, 3025 girls) in the Tokyo Child Care Center Survey consecutively recruited from 2007 to 2013 were studied. Age-and sex-specific z-scores of length/height, weight and weight for length/height were calculated relative to either the WHO standards or the Japanese 2000 Growth References (nationally representative cross sectional survey data). Compared with the WHO standards, Japanese children at birth, 1, 3, 5 years were shorter (length/height standard deviation score [SDS]-0.26,-0.82,-0.81,-0.63 for boys, and-0.15,-0.67,-0.84,-0.62 for girls, respectively) and lighter (weight SDS-0.62,-0.36,-0.34,-0.42 for boys and-0.60,-0.17,-0.29,-0.43 for girls, respectively). Weight for length/height showed smaller differences at various length/height points (SDS-0.05 to 0.15 for boys, 0.01 to 0.29 for girls, respectively). Adoption of the WHO standards would substantially alter the prevalence of short stature, underweight and overweight in Japanese children 0-5 years of age. These findings advocate the use of the national references in Japan.