1. School of West China Public Health, Sichuan University, Chengdu, PR China,
2. Chinese Evidence-based Medicine Center, West China Hospital, Sichuan University, Chengdu, PR China,
3. School of Public Health, Chengdu University of Traditional Chinese Medicine, Chengdu, PR China, and
4. West China Women’s and Children’s Hospital, Sichuan University, Chengdu, PR China