1. School of Public Policy and Administration, Xi’an Jiaotong University, Xi’an 710049, China
2. School of Public Health, Health Science Center, Xi’an Jiaotong University, Xi’an 710061, China
3. School of Elderly Care Services and Management, Nanjing University of Chinese Medicine, Nanjing 210023, China
4. Department of Health Policy and Management, Yale School of Public Health, New Haven, CT 06520, USA