Validity of self-reported weight and height: the Goiânia study, Brazil

Abstract

OBJECTIVE: To assess the validity of self-reported weight and height at the time of diagnosing obesity, and to identify the sociodemographic and individual characteristics that might be a source of information bias. METHODS: This was a cross-sectional population-based study carried out in the city of Goiânia in 2001. Interviews were conducted with 1,023 individuals aged 20-64 years, in their homes, to collect sociodemographic and self-reported weight and height information. On the same occasion, weight and height measurements were made on these individuals. The mean differences and correlation coefficients between self-reported and measured data were calculated according to age, body mass index (BMI), schooling, income and height. RESULTS: Both the men and women overestimated their heights (p<0.05), by 0.9 cm and 2.2 cm, respectively. There was no difference between self-reported and measured weights, either for the men (-0.44 kg; p=0.06) or for the women (-0.03 kg; p>;0.05). The behavior of overestimating height was influenced by age, schooling, height and body mass index. Although this index obtained from the self-reported data was underestimated (p<0.05), by 0.27 kg/m² and 0.67 kg/m² for men and women respectively, the measured and self-reported data presented a high degree of agreement. Both the sensitivity and specificity of the self-reported body mass index were high, in relation to identifying the measured index. CONCLUSIONS: In epidemiological studies for monitoring the prevalence of excess weight in populations, self-reported weights and heights constitute reliable data, which gives validity to the methodology utilized.