Trends in urban/rural inequalities in cardiovascular risk bio-markers among Chinese adolescents in two decades of urbanisation: 1991-2011.

BACKGROUND: China has seen rapid socio-economic changes and epidemiological transitions in the last few decades. Previous studies often fail to examine how wider macro-level forces contribute to changes in health inequality among its population in China. This study aims to examine urban/rural inequalities in cardiovascular (CVD) risks biomarkers among Chinese adolescents in two decades from 1991 to 2011 during the process of China's rapid urbanisation.

METHODS: Data were drawn from a nationwide longitudinal dataset of the China Health and Nutrition Survey (CHNS) (Sweeps 1991, 1993, 1997, 2000, 2004, 2006, 2009 and 2011). Children aged between 12 and 18 years (Boys: n = 3472; Girl: n = 3155) were included. A dynamic urbanisation index was created for each community (village or neighbourhood) based on community-level data that can reveal the heterogeneity within and across places and capture dimensions of social, economic and physical characteristics of urban living over time and space. Linear multilevel modeling analyses (Level 1: Occasions; Level-2: Individuals; Level-3: Households; Level-4: Communities) were performed on outcomes of CVD risk biomarkers including anthropometric measures and blood pressure.

RESULTS: After adjustment for age, maternal education and household income per capita, cardiovascular (CVD) risk biomarkers increase among Chinese adolescents during 1991 to 2011. Urbanisation tends to have an independent and positive impact on body mass index (BMI) and waist circumference for boys but not for girls. Positive interaction effect between urbanisation index and survey years for waist circumference was observed for girls (0.005; 95% confidence interval [CI], 0.002, 0.007; p < 0.01): time trends become greater when areas become more urbanized. For blood pressure, when areas become more urbanized the trends for boys become decreased (- 0.005; 95% CI, - 0.009, - 0.002; p < 0.01 for systolic blood pressure and - 0.003; 95% CI, - 0.006, - 0.001; p < 0.05 for diastolic blood pressure).

CONCLUSION: Chinese adolescents are experiencing an upward trend of cardiovascular (CVD) risks in last two decades. Its rapid urbanisation appears to further increase urban/rural inequalities in CVD risks, especially for boys from less urbanised areas and girls from more urbanised areas, which may contribute to the development of cardiovascular disease (CVD) in adulthood. It is relevant to inform policy making process to target specific vulnerable groups. Given China's urbanisation is strongly influenced by the state, there is a possibility for policy intervention to reduce inequality during the process of China's planned urbanisation.