Living Systematic Reviews.

Systematic reviews are difficult to keep up to date, but failure to do so leads to poor review currency and accuracy. "Living systematic review" (LSR) is an approach that aims to continually update a review, incorporating relevant new evidence as it becomes available. LSRs may be particularly important in fields where research evidence is emerging rapidly, current evidence is uncertain, and new research may change policy or practice decisions.This chapter describes the concept and processes of living systematic reviews. It describes the general principles of LSRs, when they might be of particular value, and how their procedures differ from conventional systematic reviews. The chapter focuses particularly on two methods of sequential meta-analysis that may be particularly useful for LSRs: Trial Sequential Analysis and Sequential Meta-Analysis, which both control for Type I error, Type II error (failing to detect a genuine effect) and take account of heterogeneity.