Funding for this research was provided by:
National Natural Science Foundation of China (71774104)
China Medical Board (16-257)
Cheeloo Youth Scholar Grant (Not applicable)
Shandong University (IFYT1810)
Received: 26 October 2021
Accepted: 15 February 2022
First Online: 19 February 2022
: This study protocol was reviewed and approved by the Ethical Committee of the Ethical Committee of School of Public Health, Shandong University (approval number, 20181228). The investigation was conducted after the acquisition of written informed consent of all participants and informed consent from guardians of the illiterate participants. All methods were carried out in accordance with relevant guidelines and regulations.
: Not applicable.
: The authors declare that they have no competing interests.