Avenues for Further Research

Overviews of reviews represent a new publication type and a new form of evidence synthesis. They have rapidly gained popularity. The development of their methodology is, however, still in its infancy. We present a bundle of areas where more work is needed in order to make overviews of reviews more valuable and reliable. Firstly, a clear-cut definition of an overview of reviews is needed. Secondly, methods of presenting the results of overviews of reviews need to be further developed. The needs of groups of users should be kept in mind, in this context, including clinicians, patients, and political decision makers. Maintaining a reasonable balance between necessary complexity and an inevitable loss of information from the reviews is a major challenge. A registration of overviews of reviews is called for. All overviews should be gathered in one freely available registry. When registering new overviews of reviews, a special note should be given to the conflicts of interests of the authors. Reporting guidelines for overviews of reviews should be prepared as soon as possible as this area lacks standardization. Furthermore, more attention should be given to different types of overviews of reviews (e.g., comparison of interventions, comparison of populations).