Table 2. Risk of bias across included studies.

Lead Author	Randomization Process	Blinding	Intention-to-treat Analysis	Missing Outcome Data	Measurement of Outcome	Selection of Reported Result	Overall Risk of Bias
Chiu 2001 [18]	High risk	High risk	Some concerns	Low risk	Some concerns	Some concerns	High risk
Chiu 2002 [20]	High risk	High risk	Some concerns	Low risk	Some concerns	Some concerns	High risk
Chiu 2009 [19]	High risk	High risk	Some concerns	Low risk	Some concerns	Some concerns	High risk
Hinarejos 2013 [17]	Low risk	Some concerns	High risk	Low risk	Some concerns	Low risk	High risk
Sprowson 2016 [16]	Some concerns	Low risk	Low risk	Low risk	Low risk	Low risk	Some concerns