Cao, Guizhen
Cui, Zhizhen
Ma, Qinghua
Wang, Congju
Xu, Yong
Sun, Hongpeng
Ma, Yana
Funding for this research was provided by:
National Natural Science Foundation of China (81402761)
the Foundation Research Project of Jiangsu Province (BK20140361)
Suzhou science and technology development project (SS201811)
Suzhou Xiangcheng district people's livelihood science and technology project (XJ201655, XJ201706)
Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases (KJS1513)
NHC Key Laboratory of Health Economics and Policy Research (Shandong University, Jinan 250012, China)
Article History
Received: 18 September 2019
Accepted: 29 July 2020
First Online: 5 August 2020
Ethics approval and consent to participate
: The Biomedical Ethics Committee of Peking University approved this survey and the conduct of the study adhered to the principles of the Declaration of Helsinki. As my study is of retrospective design, consent to participate is not required.
: No applicable.
: The authors declare that they have no competing interests.