9.1 Umbrella reviews and evidence-based practice

The volume of literature pertinent to healthcare is growing at an increasing rate, with thousands of studies published annually. Systematic reviews in healthcare have evolved in large part out of the recognition that this overwhelming amount of research evidence makes it difficult for decision makers to utilize the best available evidence to inform their decision making. Systematic reviews involve a rigorous scientific approach to an existing body of research evidence in an attempt to identify original research, critically appraise eligible studies and summarize and synthesize the results of high quality research ultimately informing a single manuscript.

A number of country-specific organizations, including the Agency for Healthcare Research and Quality (AHRQ) in the USA, the National Institute for Healthcare Excellence (NICE) in the UK, and international organizations, such as Cochrane and JBI, have dedicated themselves to the production of systematic reviews to inform healthcare policy and practice. In doing so, these organizations have contributed to the growing number of systematic reviews that have been published in recent years. Consequently, the number of systematic reviews published is, as with the bulk of scientific literature, also increasing at a phenomenal rate and now risks compounding the problem already faced by healthcare decision makers in sorting through multitudes of evidence to inform their questions. Bastian et al (2010) recently estimated that 11 systematic reviews were published every day! Still, decision-making can be challenging for healthcare practitioners and policy makers, even with systematic reviews readily available. The purpose of this chapter is to provide guidance on a method of review that can address these issues. Called an Umbrella Review, this method of review is essentially an overview of existing systematic reviews.