Table 1.

Summary of the studies included in the meta-analysis

Reference number	Author	Publication year	Country	Samples
[1]	Yu et al.	2011	China	154
[5]	Deng et al.	2013	China	115
[6]	Gai et al.	2012	China	59
[7]	Sun et al.	2012	China	59
[8]	Ding et al.	2014	China	59
[9]	Liu et al.	2013	China	311
[10]	Zhang et al.	2012	China	49
[32]	Cui et al.	2013	China	16
[33]	Wen et al.	2014	China	22