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Keywords:

  • Body mass index;
  • Box transformation;
  • longitudinal study;
  • reference value

Body mass index (BMI) is an important indicator of nutritional status. Many studies have been done to present BMI reference values in centile values rather than mean and SD values since its statistical distribution is positively skewed. Both height and weight growth charts are usually available in terms of mean and 1, 2 and 3 SD around the means; it would be of clinical value to produce BMI reference charts in a similar way. The aim of this work was to derive the mean and ±1, 2 and 3 SD BMI reference ranges as a supplement to the BMI centile reference values published previously for the same group of Swedish children. The method was based on an age-dependent Box transformation, and the β-value was given as a third-degree polynomial function over the paediatric age. The BMI reference values can be given from mathematical functions in addition to values for specific ages.

Conclusion: The BMI reference values and charts derived as described effectively reflect the nature of the variant age-dependent positive skewed statistical distribution of BMI values in the population, and can serve as a valid supplementary tool in the evaluation of growth and nutrition during paediatric years.