Socioeconomic gradient in childhood obesity and hypertension: a multilevel population-based study in a Chinese community

Background: This study aims to assess evidence for any socioeconomic gradients in childhood obesity and hypertension in a population-representative sample in Hong Kong, China. Methods: The data of a stratified random sampled growth survey collected in 2005–2006 was matched with a population by-census. Obesity was defined using the International Obesity Task Force standard and hypertension was defined using the Hong Kong norm table. Family socioeconomic status (SES) was measured by maternal education level. Neighbourhood SES was measured by median household income of the neighbourhood. Multilevel Poisson regression models with robust standard error were used to test the association. Body mass indices of children’s parents were included as potential confounders. Intra-school/neighbourhood correlations were adjusted using random factors. Results: Totally 14842 children (age 6–19 years) included in the analysis, in which 16.6% of them were overweight or obese. Children whose mother only completed secondary school or below had higher risk of childhood obesity (RR 1.41, 95% CI 1.13–1.76, p = 0.003) and hypertension (RR 1.18, 95% CI 1.01–1.36, p = 0.03). Meanwhile, children in the lowest neighbourhood SES group had higher risk of childhood underweight (RR 1.61, 95% CI 1.04–2.49, p = 0.03), overweight (RR 1.35, 95% CI 1.05–1.72, p = 0.02), and obesity (RR 2.07, 95% CI 1.11–3.88, p = 0.02). Conclusions: Socioeconomic gradient in childhood obesity and hypertension existed in Hong Kong, one of the most developed cities in China. These results have implications for policymakers and public health experts and highlight the need to monitor trends in other parts of China