Received: 4 November 2020
Accepted: 4 February 2021
First Online: 19 February 2021
Ethics approval and consent to participate
: Not applicable. Because the data we used are all from publicly published and reported data. Please refer to the references and supplementary materials.
: We are very grateful if our manuscript can be reviewed and published in “BMC Public Health”.
: We declare that we have no competing interests.