Table 3.

Risk of Bias.

Strub 2010	High risk	High risk	High risk	High risk	Low risk	Unclear risk	Unclear risk	High risk
Sletten 2015	Low risk	Low risk	High risk	Low risk	Low risk	Low risk	Unclear risk	Low risk
	Random sequence generation	Allocation concealment	Blinding of participants and personnel	Blinding of outcome assessment	Incomplete outcome data	Selective reporting	Other bias	Overall risk of bias