Validity of self-reported height and weight in 4808 EPIC–Oxford participants

TLDR

Accurate height, weight and BMI estimates can be obtained by measuring a representative sample when these factors are primary variables. The study evaluates the validity of self‑reported height and weight and the resulting BMI misclassification compared with measured values. Data from 4,808 EPIC–Oxford participants aged 35–76 were analyzed, comparing self‑reported and measured height and weight. Self‑reported height and weight showed strong correlations with measured values (r < 0.9), but men overestimated height by ~1.2 cm and underestimated weight by ~1.9 kg, leading to 22.4% and 18.0% BMI misclassification in men and women respectively, which dropped to 15.2% and 13.8% after correction, indicating that self‑reported data are generally valid for epidemiological studies.

Abstract

Abstract Objective: To assess the validity of self-reported height and weight by comparison with measured height and weight in a sample of middle-aged men and women, and to determine the extent of misclassification of body mass index (BMI) arising from differences between self-reported and measured values. Design: Analysis of self-reported and measured height and weight data from participants in the Oxford cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC–Oxford). Subjects: Four thousand eight hundred and eight British men and women aged 35–76 years. Results: Spearman rank correlations between self-reported and measured height, weight and BMI were high ( r &lt;0.9, P &gt;0.0001 ). Height was overestimated by a mean of 1.23 (95% confidence interval (CI) 1.11–1.34) cm in men and 0.60 (0.51–0.70) cm in women; the extent of overestimation was greater in older men and women, shorter men and heavier women. Weight was underestimated by a mean of 1.85 (1.72–1.99) kg in men and 1.40 (1.31–1.49) kg in women; the extent of underestimation was greater in heavier men and women, but did not vary with age or height. Using standard categories of BMI, 22.4% of men and 18.0% of women were classified incorrectly based on self-reported height and weight. After correcting the self-reported values using predictive equations derived from a 10% sample of subjects, misclassification decreased to 15.2% in men and 13.8% in women. Conclusions: Self-reported height and weight data are valid for identifying relationships in epidemiological studies. In analyses where anthropometric factors are the primary variables of interest, measurements in a representative sample of the study population can be used to improve the accuracy of estimates of height, weight and BMI.