1. Xijie Wang, Bin Dong, Yinghua Ma, Zhiyong Zou, Jun Ma, and Zhaogeng Yang are with the Institute of Child and Adolescent Health, School of Public Health, Peking University, Beijing, PR China. Sizhe Huang is with Zhongshan Health Care Centers for Primary and Secondary School, Zhongshan, PR China. Zhiqiang Wang is with the Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia.