Community context, birth cohorts and childhood body mass index trajectories: Evidence from the China nutrition and health survey 1991-2011.

Childhood overweight and obesity have shown an increase in recent birth cohorts. China has undergone rapid socioeconomic transitions accompanied by lifestyle changes that have profoundly affected the physical growth of children. Less empirical research has considered the role of community context on the cohort effects of children's body mass index (BMI) z-score trajectories. We used the mixed effect models for repeated measurements with restricted cubic spline to predict the BMI z-score trajectories in children aged 1-17 years, influenced by different birth cohorts and community context using data from the China Health and Nutrition Survey from 1991 to 2011, and stratified by sex. Results indicated that the mean of BMI z-scores of children aged 1-17 years have increased in the 2000s cohort. Community context contributed to significant differences in BMI z-score increase with age from middle childhood, and this trend of community inequalities divergences in middle childhood in recent birth cohorts. Therefore, to promote equitable growth for all children in China, policy interventions focusing on the community context may have far-reaching effects on the health of children and adolescents.