Recoding HEIGHT and WEIGHT (supplement of Anthropometry)


By: Hanneke Wijnhoven

Contact: Natasja van Schoor

Introduction
This documentation describes how height and weight are “cleaned” and imputated in order to maximize the number of (valid) measurements for these variables. We are currently working on a paper to describe this proces. Body mass index (body weight (kg) divided by height (m) squared) should be computed by the researcher. Depending on the research question, one can use height at baseline (LASA B) for all LASA cycles, or height at the corresponding LASA cycle.

Height imputed
Height was measured to the nearest 0.001 m using a stadiometer. In case no valid height measurement could be obtained due to the recorded particularities “not able to stand”, “shoes”, “kyphosis”, or “scoliosis” or height was missing one of the following imputation methods was applied:
1) a valid follow-up measurement of height was used;
2) height was calculated for those with scoliosis or kyphosis using gender-specific prediction rules based on age and knee height1 developed within the LASA sample with a valid height and knee height measurement;
3) self-reported height was used.

Knee height
Knee height of the left leg was measured at the baseline examination (1992-93) using a Mediform sliding caliper (Medical Express, Beaverton, OR, USA) with the knee and ankle joints fixed at 90° angles.

Weight imputed
Weight was measured to the nearest 0.1 kg using a calibrated bathroom scale (Seca, model 100, Lameris, Utrecht, the Netherlands). Recorded weight particularities which lead to exclusion of respondents were: “amputation”, “brace”, and “prothesis”. In addition, weight was adjusted for respectively “clothing” (-1 kg) , “corset” (-1 kg) , and “shoes” (-1 kg)(2). Self-reported weight was used when no measured weight was available. BMI was calculated as body weight (kg) divided by height (m) squared.”

* Height based on knee height
Prediction rules were developed using the LASA population with a valid height and knee height assessment, using linear regression analyses on the whole study sample, stratified by sex. Knee height and age were included in the model based on previous literature.(1)
Prediction rules based on LASA (based on study sample of n=1463)
Female: height (cm) = 68.74 – (0.16 x age) + (2.07 x knee height in cm)
Male: height (cm) = 74.48 – (0.15 x age) + (2.03 x knee height in cm)

References

  1. Chumlea WC, Roche AF, Steinbaugh ML. Estimating stature from knee height for persons 60 to 90 years of age. J Am Geriatr Soc 1985;33(2):116-20.
  2. Frank E, Dunlop AL. What does a patient's outfit weight? Fam Med 2000;32(9):595-6.