To address the possible publication bias (ie, the fact that studies with
nonsignificant results are less likely to be published), we computed the fail - safe N (Nfs) according to the method Orwin16 proposed, which is more conservative than the traditional Rosenthal Nfs.17, 18 Orwin's Nfs determines the number of additional studies in a meta - analysis
yielding null effect sizes that would be needed to
yield a «trivial» OR of 1.05.