Validity of Self-Reported Anthropometric Measures in Estimating Obesity Prevalence in Brazil: Study with Data from the National Health Survey (PNS), 2013

Abstract

Background Self-reported height and weight measurement is a simple and a non-invasive method of collecting data in population surveys. However, the inaccuracy of self-reported data may bias the population nutritional status evaluation. The aim of this study is to compare the obesity prevalence estimated with self-reported anthropometric data and with measured weight and height using data from the National Health Survey, Brazil, 2013. Methods A three-stage cluster sampling (census tracts, households, and individuals) with stratification of the primary sampling units and random selection in all stages was used to select Brazilian adults aged 18 years and over. Excluding pregnant women, measurements of weight and height were taken among all selected adults and were also self-reported during the interview on the same day. Logistic regression models were used to investigate the sociodemographic factors and lifestyles associated with the outcome "reported weight and height during the interview”. Obesity prevalence estimates calculated with self-reported and measured weight and height were compared in all variable categories. Results From the sample of 59,402 adults, 70.2% self-reported weight and height. Men were most likely to report their weight (OR = 1.14) and white people when compared to non-white (OR = 0.60). People from the upper socioeconomic class are 6.5 times more likely to report their weight and height during the interview. Healthy habits and medical consultation in the past year were significantly associated with the outcome. Among women, obesity prevalence estimated with self-reported measures (20.5%) was significantly lower than those with measured weight and height (24.4%), with larger differences among women of high socioeconomic status. No significant differences were found among men. Conclusions Given that the body mass index is used as a guide for identifying health risks, these findings indicate that direct measurement of height and weight should be performed whenever possible in Brazilian surveys to adequately support public health policies. Keywords: Health surveys; Nutritional status; Obesity; Self-reported anthropometric measures.