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Prediction of total body water in infants and children
  1. J C K Wells1,
  2. M S Fewtrell1,
  3. P S W Davies2,
  4. J E Williams1,
  5. W A Coward3,
  6. T J Cole4
  1. 1MRC Childhood Nutrition Research Centre, Institute of Child Health, London, UK
  2. 2Children’s Nutrition Research Centre, Department of Paediatrics and Child Health, University of Queensland, Royal Children’s Hospital, Brisbane, Australia
  3. 3MRC Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge, UK
  4. 4Centre for Paediatric Epidemiology and Biostatistics, Institute of Child Health, London, UK
  1. Correspondence to:
    Dr J C K Wells
    MRC Childhood Nutrition Research Centre, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK; J.Wellsich.ucl.ac.uk

Abstract

Background: In paediatric clinical practice treatment is often adjusted in relation to body size, for example the calculation of pharmacological and dialysis dosages. In addition to use of body weight, for some purposes total body water (TBW) and surface area are estimated from anthropometry using equations developed several decades previously. Whether such equations remain valid in contemporary populations is not known.

Methods: Total body water was measured using deuterium dilution in 672 subjects (265 infants aged <1 year; 407 children and adolescents aged 1–19 years) during the period 1990–2003. TBW was predicted (a) using published equations, and (b) directly from data on age, sex, weight, and height.

Results: Previously published equations, based on data obtained before 1970, significantly overestimated TBW, with average biases ranging from 4% to 11%. For all equations, the overestimation of TBW was greatest in infancy. New equations were generated. The best equation, incorporating log weight, log height, age, and sex, had a standard error of the estimate of 7.8%.

Conclusions: Secular trends in the nutritional status of infants and children are altering the relation between age or weight and TBW. Equations developed in previous decades significantly overestimate TBW in all age groups, especially infancy; however, the relation between TBW and weight may continue to change. This scenario is predicted to apply more generally to many aspects of paediatric clinical practice in which dosages are calculated on the basis of anthropometric data collected in previous decades.

  • anthropometry
  • body composition
  • total body water
  • obesity
  • clinical practice

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