Funding for this research was provided by:
Social Sciences Foundation of Liaoning Province (No. L18ATJ001)
Received: 16 June 2019
Accepted: 19 February 2020
First Online: 27 February 2020
Ethics approval and consent to participate
: All procedures in our study were approved by the Ethical Committee Group of China Medical University (CMU6206–1004). Written informed consent was obtained from each participant, each school and nursing homes.
: Not applicable.
: The authors declare that they have no competing of interests.