Change in bias in self-reported body mass index in Australia between 1995 and 2008 and the evaluation of correction equations - PubMed (original) (raw)

Change in bias in self-reported body mass index in Australia between 1995 and 2008 and the evaluation of correction equations

Alison J Hayes et al. Popul Health Metr. 2011.

Abstract

Background: Many studies have documented the bias in body mass index (BMI) determined from self-reported data on height and weight, but few have examined the change in bias over time.

Methods: Using data from large, nationally-representative population health surveys, we examined change in bias in height and weight reporting among Australian adults between 1995 and 2008. Our study dataset included 9,635 men and women in 1995 and 9,141 in 2007-2008. We investigated the determinants of the bias and derived correction equations using 2007-2008 data, which can be applied when only self-reported anthropometric data are available.

Results: In 1995, self-reported BMI (derived from height and weight) was 1.2 units (men) and 1.4 units (women) lower than measured BMI. In 2007-2008, there was still underreporting, but the amount had declined to 0.6 units (men) and 0.7 units (women) below measured BMI. The major determinants of reporting error in 2007-2008 were age, sex, measured BMI, and education of the respondent. Correction equations for height and weight derived from 2007-2008 data and applied to self-reported data were able to adjust for the bias and were accurate across all age and sex strata.

Conclusions: The diminishing reporting bias in BMI in Australia means that correction equations derived from 2007-2008 data may not be transferable to earlier self-reported data. Second, predictions of future overweight and obesity in Australia based on trends in self-reported information are likely to be inaccurate, as the change in reporting bias will affect the apparent increase in self-reported obesity prevalence.

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Figures

Figure 1

Figure 1

Reporting error in height and weight (population-weighted) for men and women by deciles of measured height and weight, determined from Australian NHS in 1995 and 2007-2008; a. height error in men; b. height error in women; c. weight error in men; d. weight error in women.

Figure 2

Figure 2

Reporting error in height and weight (population-weighted) for men and women by age, determined from Australian NHS in 1995 and 2007-2008; a. height error in men; b. height error in women; c. weight error in men; d. weight error in women.

Figure 3

Figure 3

Mean BMI by age and sex (population-weighted) using measured height and weight (NHS), self-reported height and weight (NHS) and corrected height and weight using correction equations applied to self-reported data.

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