Topic duplication and research waste at the ‘Overviews of systematic reviews’ level: Survey of overlapping overviews

Abstract Background Multiple overviews of systematic reviews conducted on the same topic (“overlapping overviews”) represent a waste of research resources and can confuse or mislead clinicians and policymakers. We aimed to assess the frequency and characteristics of published overviews addressing the same clinical question or topic. Methods We used MEDLINE, Epistemonikos and Cochrane databases to locate overviews that: focused on synthesising reviews; conducted systematic searches; had a methods section; and examined a health intervention or clinical treatment. We then determined which overviews addressed the same or overlapping populations/settings, interventions, and outcomes [PIO]). Overlap in topic was defined as: duplication of PIO elements, not representing an update of a previous overview, and not a replication for quality purposes. Results Of 541 overviews located (2000–2018), 178 (33%) overlapped with another overview addressing a similar PIO. The topics of overlapping overviews fell within 13 WHO ICD-10 medical classifications, and there were 65 overlapping topics in total. The most prevalent topic with overlap across 7 overviews was smoking cessation (pharmacologic and non-pharmacologic interventions). Five overlapping overviews related to acupuncture for pain, 5 addressed cannabinoids for pain and symptoms, and 5 addressed exercise for bone and muscle health. For 15/65 (22%) of these topics, one author was involved in at least two of the overlapping overviews. Conclusions We found significant duplication and unnecessary overlap across overviews. To avoid waste and redundancy, protocols of overviews should be registered in a targeted database, and overviews should cite other studies on similar topic with a rationale.