Funding for this research was provided by:
the Swedish Research Council and the National Natural Science Foundation of China joint project (81361138019, 540-2013-8797)
Received: 6 May 2020
Accepted: 9 July 2020
First Online: 18 July 2020
Ethics approval and consent to participate
: The study was approved by the Medical Institutional Review Board of the School of Public Health of Fudan University (approval No. IRB 2015-09-0565) and written informed consent was received from each participant.
: Not applicable.
: The authors declare that they have no competing interests.