Overviews of Reviews: Concept and Development

Background: In the last years, overviews of systematic reviews, or umbrella reviews, have seen a dramatic increase in their use. An overview aims to provide a summary of the included reviews and will often examine research questions beyond those addressed in the systematic reviews being synthesised. The purpose of this article is to provide some recommendations on how overviews should be conducted and reported. Method: A literature review was performed to identify relevant papers on both methodological and applied overviews. Results: The current literature recommends carrying out overviews by following similar steps to those of systematic reviews: (a) Defining the overview research question; (b) inclusion and exclusion criteria; (c) literature search; (d) data extraction; (e) assessment of risk of bias and reporting quality; (f) overview results; and (g) reporting the overview. Of special interest is how to address dependencies between the systematic reviews. Conclusions: Overviews allow evidence to be efficiently combined from multiple systematic reviews. This offers the possibility of translating and summarizing large amounts of information. As in primary studies and systematic reviews, conducting and reporting of overviews must meet appropriate quality standards.