Limitations
There are a number of limitations to our review. Relevant articles might
be missed because the search was conducted only in three databases, in
one language, and excluded grey literature. One article about the
protective effect of ginkgo biloba extract on CiO was retrieved by the
manual research on clinicaltrial.gov, but wasn’t available in its
full-text format. The conclusions of our review are based on studies
with small and heterogeneous samples, who were followed on different
time ranges, and whose analysis had low quality, so our results should
be taken as preliminary findings that need to be corroborated in the
future. None of the trials took into account patients’ quality of life
or reported outcomes to assess the intervention’s benefit. So a
comprehensive understanding of the effectiveness of any intervention is
missing. Finally, the safety outcomes of the interventions were not
mentioned in 10 out of 23 studies. Since most of the interventions
contain mild benefits and uncertain risks, underreporting of side
effects limits the power of our conclusions.