Conclusion

Abstract

An ongoing challenge looms for all scholars and decision-makers due to the momentous increase in the breadth of evidence focusing on important decisions. This is typical of the current era dominated by information, access, and participation. Modern information tools to access and exploit this wealth of data, such as online databases, reference management software, and online data repositories, offer a unique opportunity to maximize the scientific and practical yield of available evidence. However, these instruments must be mastered competently, and the resulting pieces of evidence have to be appraised with full awareness of their strengths and weaknesses. Indeed, decision-makers must be able to appropriately use a variety of study designs in alternating settings or for different goals, without limiting their scope to a single one. We cannot narrow our attention to randomized trials or meta-analyses, in as much as we cannot rely solely on case reports. Moving from individuals to studies combining several groups of people and to reviews combining several trials, umbrella reviews and overviews of reviews represent an additional and even more generalizing stage of evidence synthesis. Despite their novelty, their role in the hierarchy of evidence is becoming more and more established. Even in the most challenging settings (e.g., when the evidence base is inconclusive, inconsistent, or incoherent), meta-epidemiologic studies may provide uniquely original and comprehensive perspectives on important issues and may thus indirectly guide both research and practice. Despite the milestones already met in this field of evidence synthesis, further developments are eagerly awaited and will surely enable more careful design, conduct, and reporting of umbrella reviews, overviews of reviews, and meta-epidemiologic studies, hopefully leading to more accurate and prolific results.