Risk of Bias
Figure 2 presents the results of the risk-of-bias assessment for each
study separately, and Figure 3 summarizes the percentages of studies
with low, unclear, and high risks of bias. The risk of bias of included
trials was high or unclear for most domains (Figure 2). Random sequence
generation was adequately described in 5 trials (56%) and unclear in 4
trials (44%). Allocation concealment was assessed as low risk of bias
in 3 trials (33%), high risk of bias in 1 trial (11%) and unclear in
the remaining 5 trials (56%). Of the 9 trials, three trials (33%)
blinded the participants to the trial intervention, high risk of bias in
only 1 trail (11%) and unclear in 5 trial (56%). Blinding of outcome
assessors occurred in 4 trials (44%), high risk in 1 trial (11%) and
unclear in 4 (44%). Six trials (67%) were considered as low risk of
attrition bias and 11 trials (33%) were assessed as high risk. All
trials (100%) were assessed to have low reporting bias. Eight trials
(89%) were assessed as having low risk of other potential bias and
unclear in 1 (11%). Overall methodological quality of evidence was
considered fair. We were unable to assess publication bias due to the
limited number of trials.