Wang, Yi
Li, Jie
Fu, Peipei
Jing, Zhengyue
Zhao, Dan
Zhou, Chengchao
Article History
Received: 23 March 2021
Accepted: 14 February 2022
First Online: 28 February 2022
Declarations
:
: Before each survey, we obtained the written informed consents from each respondents stating the study purposes, value, methods, and potential risks. For illiterate older people, in addition to obtaining their verbal consent, we also require their legally/kin authorized representative to provide a proxy written informed consent. This study was reviewed and approved by the Ethics Committee of Shandong University (approval No. 20181228) in accordance with the Declaration of Helsinki.
: Not applicable.
: The authors declare that they have no conflicts of interest.