Effects of urbanization on metabolic syndrome via dietary intake and physical activity in Chinese adults: Multilevel mediation analysis with latent centering

Abstract

Rationale: China has undergone rapid urbanization in the past decades. Metabolic syndrome refers to a cluster of cardiometabolic risk factors such as abdominal obesity, raised blood pressure, and elevated glucose. Existing studies have not explicitly examined the urbanization effect on metabolic syndrome. Objective: The present study aims to examine the temporal effects of urbanization on metabolic syndrome in the Chinese context and evaluate dietary intake and physical activity as potential mediating factors. Method: The study sample comprised 6,217 Chinese adults aged between 30 and 65 recruited in 218 communities from 2000 to 2009 waves of the China Health and Nutrition Survey. Growth in urbanization of the communities was derived using latent growth modeling on continuous urbanization index from 2000 to 2009. The participants reported their physical activity and dietary intake. Body mass index and biomarkers were measured at 2009 for diagnosis of metabolic syndrome. Multilevel mediation analysis with novel latent centering approach was conducted across gender to evaluate direct and indirect effects of urbanization on metabolic syndrome via changes in dietary intake and physical activity. Results: The sample displayed linear increasing trends in urbanization, intakes of red meat, dairy products and fast food and declining cereal intake and physical activity with significant inter-individual variations. Controlling for individual-level and community-level covariates, urbanization showed a positive but non-significant direct effect on metabolic syndrome across gender. There were significant and positive indirect effects from urbanization to metabolic syndrome via changes in physical activity in males and via changes in fast food intake in females. Conclusions: The present results highlight the health impact of urbanization as a dynamic process at the community level on metabolic syndrome via different indirect pathways of lifestyle factors across gender. Methodological and practical implications are discussed in relation to these modifiable lifestyle factors in the urbanizing Chinese society.