Table 2.

Summary of Risk Assessment of Bias in Individual Studies (n = 26)

Author (year), Country	Risk of bias in individual studies
Baranova et al. (2018), Czech Republic	Low
Li et al. (2018), China	Low
Lin et al. (2017), China	Low
Lin et al. (2017), China	Low
Zhang et al. (2016), China	Moderate
Deng et al.(2016), China	Low
Lin et al. (2015), China	Low
Lin et al. (2015), China	Low
Deng et al. (2014), China	Low
Lin et al. (2014), China	Low
Lin et al. (2014), China	Low
Lin et al. (2014), China	Low
Luo et al. (2014), China	Low
Niu et al. (2014), China	Low
Wang et al. (2014), China	Low
Wang et al. (2014), China	Low
Danese et al. (2013), Italy	Low
Fang (2013), China	Low
Lin (2013), China	Low
Zhang et al. (2012), China	Low
He et al.(2012), China	Low
Lin et al. (2012), China	Low
Tang et al.(2012), China	Moderate
Haruki et al. (2010), Japan	Low
Yu et al. (2010), China	Low
Yu et al. (2009), China	Moderate