Table 2.

Risk of bias of included studies based on the Cochrane Collaboration’s tool for assessing risk of bias

Study	Publication year	Random sequence generation	Allocation concealment	Blinding of participants and personnel	Blinding of outcome assessment	Incomplete outcome data	Selective reporting	Other bias	Total risk of bias
Ambrosino et al. [16]	1981	Low	Unclear	Unclear	Unclear	Low	Low	Low	Low
Tiep et al. [17]	1986	Low	Unclear	Unclear	Unclear	Low	Low	Low	Low
Collins et al. [18]	2003	Low	Unclear	Unclear	Unclear	Low	Low	Low	Low
Jones et al. [19]	2003	Low	Unclear	Unclear	Unclear	Low	Low	Low	Low
Garrod et al. [20]	2005	Low	Unclear	Low	Low	Low	Low	Low	Low
Spahija et al. [21]	2005	High	High	Unclear	Unclear	Low	Low	Unclear	High
Nield et al. [22]	2007	Low	Unclear	Unclear	Unclear	Low	Low	Low	Low
Collins et al. [23]	2008	Low	Unclear	Unclear	Unclear	Low	Low	Low	Low
Faager et al. [24]	2008	Low	High	Unclear	Unclear	Low	Low	Unclear	High
Bonilha et al. [25]	2009	Low	Unclear	Unclear	Unclear	Low	Low	Low	Low
Lord et al. [26]	2010	Low	Low	Unclear	Low	Low	Low	Unclear	Low
Lin et al. [27]	2012	Low	Unclear	Unclear	Unclear	Low	Low	Low	Low
Lord et al. [28]	2012	Low	Low	Low	Low	Low	Low	Low	Low
van Gestel et al. [29]	2012	Low	Unclear	Unclear	Low	Low	Low	Low	Low
Yamaguti et al. [30]	2012	Low	Unclear	Unclear	Low	Low	Low	Low	Low
Bhatt et al. [31]	2013	Low	Unclear	Unclear	Low	Low	Low	Low	Low
de Araujo et al. [32]	2015	Low	Unclear	High	High	Low	Low	Unclear	High
Borge et al. [34]	2015	Low	Low	Low	Low	Low	Low	Low	Low
Cabral et al. [33]	2015	Low	Low	High	Low	Low	Low	Unclear	Low