Overview of systematic reviews: not just another review design

We live in a new era of information, where the number of academic publications has reached exponential growth without precedent. This may be beneficial to all of us, but excess information without a clear synthesis can lead to uncertain conclusions that hinder clinical, research and policy progress. In BJSM alone, more than 400 systematic reviews (SRs) have been published in the past decade. In this context, overview of SRs (OSRs) are a newer form of evidence synthesis that aim to summarise the current evidence for a specific topic or answer a new question using the synthesis of multiple SRs. The general purpose of OSRs is to synthesise SRs that are conducted on subpopulations, use varying interventions on a specific outcome or measure different outcomes on a specific intervention/treatment of interest. In addition, OSRs may sometimes evaluate evidence from supplemental primary studies (eg, observational studies or randomised controlled trials) in situations where previous SRs are incomplete or out of date.1 OSRs are valuable in that they can address research questions with a broader scope than SRs because SRs are the primary unit of analysis. Moreover, OSRs can provide summaries of …