Protocol-based Umbrella Review — Pre-registered Overview of Systematic Reviews

A protocol-based umbrella review is an umbrella review — a synthesis of existing systematic reviews and meta-analyses on a common topic — conducted under a publicly pre-registered protocol, typically in PROSPERO or a similar registry. Pre-registering the protocol before data collection begins commits the research team to prospectively defined eligibility criteria, search strategy, appraisal tools, and synthesis methods, sharply reducing the risk of outcome reporting bias and post-hoc analytical flexibility.