Journal Article

BMI-related errors in the measurement of obesity

Rothman, K.J

2008

Overview

Body mass index (BMI) has various deficiencies as a measure of obesity, especially when the BMI measure is based on self-reported height and weight. BMI is an indirect measure of body fat compared with more direct approaches such as bioelectrical impedance. Moreover, BMI does not necessarily reflect the changes that occur with age. The proportion of body fat increases with age, whereas muscle mass decreases, but corresponding changes in height, weight and BMI may not reflect changes in body fat and muscle mass. Both the sensitivity and specificity of BMI have been shown to be poor. Additionally, the relation between BMI and percentage of body fat is not linear and differs for men and women. The consequences of the errors in the measurement of obesity with BMI depend on whether they are differential or nondifferential. Differential misclassification, a potentially greater problem in case-control and cross-sectional studies than in prospective cohort studies, can produce a bias toward or away from the null. Nondifferential misclassification produces a bias toward the null for a dichotomous exposure; for measures of exposure that are not dichotomous, the bias may be away from the null. In short, the use of BMI as a measure of obesity can introduce misclassification problems that may result in important bias in estimating the effects related to obesity.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: accuracy / Adipose tissues / Age / Age Factors / Bias / body composition / Body fat / Body Mass Index / body weight / Cohort analysis / Cross-sectional studies / Diagnosis / Diagnosis, Differential / disease diagnosis / Epidemiology / Female / gender differences / Health aspects / Health Promotion and Disease Prevention / height / Humans / Impedance / Internal Medicine / literature reviews / Male / measurement / Medicine / Medicine & Public Health / men / Metabolic Diseases / Middle Aged / Obesity / Obesity - diagnosis / Obesity - mortality / original-article / Physiological aspects / Properties / Public Health / reliability / Self Disclosure / Self report / Sensitivity and Specificity / Sex Factors / temporal variation / test sensitivity / test specificity / Women