1. From the Department of Paediatrics, the Centre for Clinical Trials and Epidemiology Research, and the Department of Orthopaedics and Traumatology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong; the Department of Nutrition and Food Hygiene, Sen Yat Sen University of Medical Sciences, Guangzhou; and the Jiangmen Epidemic Station, Jiangmen, Guangdong Province, China.