Table 2.

Study qualities determined based on the Cochrane Risk of Bias Tool

	Random sequence generation (selection bias)	Allocation concealment (selection bias)	Blinding of participants and personnel (performance bias)	Blinding of outcome assessment (detection bias)	Incomplete outcome data (attrition bias)	Selective reporting (reporting bias)	Other bias
Focht et al., 2017 [39]	+	+	-	+	+	+	+
Foo et al., 2020　[41]	+	+	-	+	?	?	+
Gay et al., 2020 [42]	+	+	-	+	?	+	+
Helminen et al., 2015 [43]	+	+	+	+	+	+	+
Somers et al., 2012 [40]	+	?	-	+	+	?	+
Yip et al., 2007 [37]	+	?	-	?	-	?	+
Yip et al., 2008 [38]	+	?	-	?	-	?	+

(+) low risk of bias, (?) unclear risk of bias, (-) high risk of bias