Height and weight among 7 – 18 years old urban and rural primary and high school students in Sichuan province: a cross-sectional analysis with LMS method

  Objective  To construct percentile curves for height and weight of child and adolescent students using coefficient of skewness-median-coefficient of variation – Lambda-Mu-Sigma (LMS) method and to analyze rural urban difference in growth and development of the students for the application of LMS method in relevant researches.

  Methods  Using cluster random sampling, we selected 25 475 students aged 7 – 18 years in 110 primary and high schools in urban and rural regions across Sichuan province in 2018. Based on the data of height and weight measurement, the 5th, 50th and 95th percentile (P₅, P₅₀ and P₉₅) curves for the urban and rural students were constructed using LMS method with the software (LMS chartmaker Light Version 2.54) and the differences between the urban and rural students with the height and weight of P₅, P₅₀ and P₉₅ values were analyzed.

  Results  The urban and rural differences in average height for the boy students with the P₅, P₅₀ and P₉₅ value were 0.03, 1.20 and 1.60 cm, and those for the girl students were – 0.32, 0.88 and 0.95 cm; while, the urban and rural differences in average weight for the boy students with the P₅, P₅₀ and P₉₅ value were 0.18, 0.96 and 1.85 kg, and those for the girl students were – 0.25, 0.29 and 1.55 kg, respectively.

  Conclusion  For the child and adolescent students in Sichuan province, the urban and rural difference in average height and weight are larger in the boy students than in the girl students and both the differences are larger in the students with higher percentile values than in the students with lower percentile values. For the students with 50th and 95th percentile value of height and weight, the urban and rural differences increase first and then decrease with the increment of the sutdents′ age.