Strengths and limitations
The strengths of this systematic review and meta-analysis were: i)
applying a comprehensive search strategy; ii) taking the explicit
criteria for inclusion of interested studies; iii) using strict
statistical methods for analyses; iv) employing the preferred
methodology of systematic review and meta-analysis;21,
22 v) performing the test of publication bias with multiple methods.
The limitations of this study were also impossible to ignore, including
that: i) the pooled RR was synthesized from the results of observational
studies which presented plausible confounding factors decreasing the
strength of observed effect. Therefore, the findings should be
interpreted with caution; ii) a high degree of heterogeneity was
presented, which can’t be interpreted from a single study because the
sensitivity analyses using a leave-one-out method didn’t change the
direction of effect. In this study, the origin of heterogeneity may
mainly result from the study design, i.e. the low heterogeneity in the
prospective studies. However, other factors like races of patients,
follow-up duration, the observational window, may importantly impact the
heterogenous effects of OAC use on risk of dementia.