Seeing the forest (plot) for the trees-the importance of evidence synthesis in older adult care.

Systematically reviewing all the available evidence and then creating summary analyses of the pooled data is the foundation of evidence-based practice. Indeed, this evidence synthesis approach informs much of the care of older adults in hospital and community. It is perhaps no surprise that the journal Age and Ageing is a frequent platform for publishing research papers based on systematic review and synthesis. This research has evolved substantially from the early days of evidence-based medicine and the Cochrane Collaboration. The traditional approach would be a quantitative summary, calculated using pair-wise meta-analysis of randomised controlled trials of drug versus placebo, or a synthesis of observational studies to create summaries of prevalence, associations and outcomes. Methods have evolved and newer techniques such as scoping reviews, test accuracy meta-analysis and qualitative synthesis are all now available. The sophistication of these methods is driven in part by the increasingly complex decisions that need be made in contemporary older adult care. Age and Ageing continues to champion established and novel evidence synthesis approaches, and in the accompanying Collection exemplars of these differing methods are presented and described. Whilst there is marked heterogeneity in the techniques used, the consistent and defining feature of all these papers is the desire to comprehensively, and critically summarise the evidence in order to answer the most pertinent questions regarding older adult care.