Table 2.

Summary of risk‐of‐bias assessment among the included studies

	Selection bias		Reporting bias	Performance bias	Detection bias	Attrition bias
	Random sequence generation	Allocation concealment
Kumada et al8	Unclear	Low	Unclear	Low	Low	Low
Nishizawa et al9	Low	Unclear	Unclear	Unclear	Unclear	Unclear
Takao et al (2015)10	Unclear	Unclear	Unclear	High	High	Unclear

According to the Cochrane Handbook for Systematic Review of Intervention.