Table 2. Risk of bias assessment.

Author/year	Random sequence generation	Allocation concealment	Blinding of participants and researchers	Blinding of outcome assessment	Incomplete outcome data	Selective reporting
Neuman et al., 2016 [13]	Unclear	Unclear	Low	Unclear	Low	Low
Sendur et al., 2014 [11]	Unclear	Unclear	High	Unclear	Low	Low
Zepeda et al., 2012 [20]	Unclear	Unclear	High	Unclear	Low	Low
Espinola-Klein et al., 2011 [21]	Unclear	Unclear	Low	Unclear	Low	Low
Fedorishina et al., 2010 [22]	Unclear	Unclear	Unclear	Unclear	Low	Low
Pronko et al., 2009 [14]	Low	Unclear	High	Unclear	Low	Low
Simova et al., 2009 [26]	Unclear	Unclear	Low	Unclear	Low	Low
Pasini et al., 2008 [23]	Unclear	Unclear	Low	Unclear	Low	Low
Ghiadoni et al., 2003 [24]	Unclear	Unclear	High	Unclear	Low	Low
Tzemos et al., 2001 [25]	Unclear	Unclear	Low	Unclear	Low	Low