Wednesday, July 15, 2020

The Median Cochrane Systematic Review Takes 2 Years to Publish, but This Window May be Lengthening

Recent posts (1, 2, 3, 4) have discussed the use of machine learning, automation, crowdsourcing, and other strategies that can substantially speed up the process of a systematic review. However, for most systematic review authors in the year 2020, a project with a timeline on the order of weeks or months – as opposed to years – remains a far-off futuristic ideal.

In fact, according to a recently published review analyzing over 6,700 systematic reviews published in the Cochrane Database since 1995, the median systematic review took 2 years from the publication of the protocol to the resulting review. Reviews published over the past decade alone, however, took a median 2.4 months longer than this, suggesting that the window of time from protocol to publication is increasing. Additionally, the majority (60%) of reviews published over the past five years took longer than two years to complete, compared with just over half (51%) of all reviews analyzed. This is an important finding, as with a longer lag time comes a greater risk of the review becoming out-of-date before it even has the chance to be disseminated.

A figure from Andersen et al. compares the Kaplan-Meier curve of turnaround times for Cochrane reviews published within each 5-year interval, with marked slowdown for the most recent cohort (2015-2019). Click to enlarge.

There was also a high amount of variability in turnover time between different Review Groups, with the fastest group publishing reviews 2.6 times faster than the slowest.

As Anderson and colleagues explain, it is worth noting that Cochrane reviews tend to take longer to publish than other systematic reviews, perhaps due to their higher standards of rigor. However, the median publication time appears to have increased over the latter half of the last quarter-century – perhaps due to the increasing complexity and rigors of reporting systematic reviews in addition to the complexity of the studies they are charged with analyzing.

Thus, although technological advancements may someday shorten the timeline of the typical systematic review, the data suggest that the turnaround time has only increased in recent years. Qualitative research comparing the workflow and processes of the different Cochrane review groups may provide insight into best practices for improving the efficiency of a systematic review’s production, and with it, the currency of its findings upon publication.

Andersen, M.Z., G├╝len, S., Fonnes, S., Andresen, K., & Rosenberg, J. Half of Cochrane reviews were published more than 2 years after the protocol. J Clin Epidemiol, 2020; 124: 85-93.

Manuscript available from the publisher's website here.