Socioeconomic inequality in childhood obesity and its determinants: a Blinder-Oaxaca decomposition

Childhood obesity has become a priority health concern worldwide. Socioeconomic status is one of its main determinants. This study aimed to assess the socioeconomic inequality of obesity in children and adolescents at national and provincial levels in Iran.

This multicenter cross-sectional study was conducted in 2011-2012, as part of a national school-based surveillance program performed in 40,000 students, aged 6-18-years, from urban and rural areas of 30 provinces of Iran. Using principle component analysis, the socioeconomic status of participants was categorized to quintiles. Socioeconomic status inequality in excess weight was estimated by calculating the prevalence of excess weight (i.e., overweight, generalized obesity, and abdominal obesity) across the socioeconomic status quintiles, the concentration index, and slope index of inequality. The determinants of this inequality were determined by the Oaxaca Blinder decomposition.

Overall, 36,529 students completed the study (response rate: 91.32%); 50.79% of whom were boys and 74.23% were urban inhabitants. The mean (standard deviation) age was 12.14 (3.36) years. The prevalence of overweight, generalized obesity, and abdominal obesity was 11.51%, 8.35%, and 17.87%, respectively. The SII for overweight, obesity and abdominal obesity was -0.1, -0.1 and -0.15, respectively. Concentration index for overweight, generalized obesity, and abdominal obesity was positive, which indicate inequality in favor of low socioeconomic status groups. Area of residence, family history of obesity, and age were the most contributing factors to the inequality of obesity prevalence observed between the highest and lowest socioeconomic status groups.

This study provides considerable information on the high prevalence of excess weight in families with higher socioeconomic status at national and provincial levels. These findings can be used for international comparisons and for healthcare policies, improving their programming by considering differences at provincial levels.