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Assessment of Child Anthropometry in a Large Epidemiologic Study
09:36

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Published on: February 2, 2017

Methodological problem with comparing increases in different measures of body weight.

Helen L Walls1, Anna Peeters, Haider Mannan

  • 1Department of Epidemiology & Preventive Medicine, Monash University, Alfred Hospital, Victoria 3004, Australia. helen.walls@anu.edu.au.

BMC Research Notes
|May 24, 2011
PubMed
Summary

Directly comparing percentage changes in waist circumference (WC) and body mass index (BMI) is flawed. Accurate comparisons require accounting for the relationship between WC and BMI using regression analysis.

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Area of Science:

  • Anthropometry
  • Public Health
  • Biostatistics

Background:

  • Previous studies have compared proportional increases in waist circumference (WC) and body mass index (BMI) over time.
  • This comparative method is statistically flawed due to the inherent relationship between WC and BMI.
  • Understanding this relationship is crucial for accurate health trend analysis.

Purpose of the Study:

  • To explain the statistical limitations in comparing proportional changes in WC and BMI.
  • To demonstrate the necessity of considering the WC-BMI relationship in trend analyses.
  • To provide a statistically sound method for comparing changes in anthropometric measures.

Main Methods:

  • Utilized data from two US cross-sectional surveys: NHANES (1988-94 and 2005-06).
  • Calculated the percentage change in average BMI and average WC between the survey periods.
  • Employed regression analysis to examine changes in WC relative to BMI, accounting for the intercept term.

Main Results:

  • Crude percentage change in BMI (5.8%) was slightly higher than WC (5.1%).
  • Direct comparison of these percentages is invalid because the regression equation relating WC and BMI has a non-zero intercept.
  • The regression coefficient of time indicates whether WC has increased disproportionately relative to BMI.

Conclusions:

  • Direct percentage change comparisons between WC and BMI are not informative.
  • Accurate comparisons necessitate incorporating the established regression relationship between WC and BMI.
  • Regression analysis provides a valid framework for assessing changes in anthropometric measures over time.