Evidence Synthesis Methods in Health Research

Evidence synthesis encompasses a spectrum of methodological approaches designed to assemble, appraise and integrate findings from primary studies in order to inform health policy, clinical practice and future research agendas. At its core lie systematic reviews, which use predefined protocols to identify and critically appraise all relevant evidence on a focused question, often supplemented by meta-analysis to yield pooled effect estimates. Scoping reviews have emerged as a complementary approach for mapping broad research landscapes, clarifying concepts, identifying evidence gaps and guiding the formulation of precise questions for subsequent systematic reviews. Mapping reviews extend scoping methods by producing visual representations or interactive evidence and gap maps that juxtapose interventions, outcomes and study designs. Rapid reviews introduce methodological shortcuts to meet time-sensitive decision-making needs, while network meta-analyses allow comparison of multiple interventions in a single statistical framework. Across all approaches, rigorous search strategies, transparent selection criteria, risk-of-bias assessment and stakeholder engagement underpin the trustworthiness and utility of the synthesis. Recent methodological innovation has focused on standardising reporting guidelines, enhancing reproducibility, incorporating grey literature and leveraging digital tools for living reviews that are continually updated as new evidence emerges. The global significance of these methods is reflected in their ability to inform guideline development, allocate research funding and optimise health system performance by synthesising vast and heterogeneous bodies of evidence into coherent, actionable conclusions.

Research from Nature Portfolio

No recent Nature Portfolio content available.

Evidence Synthesis Methods in Health Research publication trend

The graph below shows the total number of articles in evidence synthesis methods in health research across all publications each year (not limited to Nature Index journals).

Technical terms

Systematic review: A structured approach to identify, appraise and synthesise all relevant studies on a defined question using a predefined protocol.

Scoping review: A broad mapping exercise to explore the extent, range and nature of research activity, often to clarify concepts and identify gaps.

Mapping review: A method to chart and categorise existing evidence across interventions and outcomes, frequently producing visual or interactive maps.

Evidence and gap map (EGM): A matrix or web-based tool that summarises available evidence across key domains (e.g., intervention by outcome), highlighting areas lacking sufficient research.

Meta-analysis: A statistical technique that combines quantitative results from multiple studies to estimate overall effect sizes and assess consistency across studies.

References

1. PROTOCOL: Methods used in the development, production and updating of evidence and gap maps: A scoping review. Campbell Systematic Reviews (2024).
2. Advancing the methodology of mapping reviews: A scoping review. Research Synthesis Methods (2024).
3. What is an evidence map? A systematic review of published evidence maps and their definitions, methods, and products. Systematic Reviews (2016).
4. Scoping reviews: reinforcing and advancing the methodology and application. Systematic Reviews (2021).