Funding for this research was provided by:
Financial support comes from Shandong Provincial Natural Science Foundation, China (ZR2013GM023)
Article History
First Online: 8 May 2020
Compliance with Ethical Standards
:
: Financial support was received from Shandong Provincial Natural Science Foundation, China (ZR2013GM023).
: Tong Liu, Shunping Li, Min Wang, Qiang Sun, and Gang Chen declare no conflicts of interest.
: Ethical approval (reference no. 20131002) was obtained from the Ethics Review Board of the School of Public Health, Shandong University. This research adhered to the tenets of the Declaration of Helsinki.
: Informed consent was obtained from all individual participants included in the studies.