Capturing the influx of living systematic reviews: a systematic methodological survey

Living systematic reviews (LSRs) are an emerging type of review that continuously updates as new evidence becomes available. A previous methodological survey conducted in 2021 identified and studied all health-based LSRs. Since then, the landscape has changed, including the on-going accumulation of COVID-19 research and availability of automation tools. Furthermore, various methods and guidance exist for conducting LSRs and review authors are often encouraged to explore opportunities to maximize dissemination. We conducted an LSR survey update to describe LSRs in a "post-COVID" era. Our objectives were to summarize the uptake of LSRs, describe their characteristics, including methodological and communicative characteristics, and identify patterns in LSR attributes.

We systematically searched for new LSRs and any updates-including updates from LSRs identified previously-published between May 2021 and March 2023 in any health field. Eligible articles were identified and data extracted and combined with data from the original survey. Outcomes broadly included LSR characteristics and uptake, and methodological and communicative characteristics. Analyses were descriptive and included visualizations to explore distributions, combinations, and any time effects of characteristics.

A total of 549 records across 168 individual LSRs were identified (of which 92 LSRs were newly detected). Although the presence of COVID-19 LSRs dominated in later years, there was an increased uptake in non-COVID-19 LSRs; the former were found to search the evidence and update/publish results more frequently. Where reported, the approach to conducting updates varied considerably, including a wide range of prespecified frequencies and/or triggers. Of the 337 updates, 25.5% reported on ongoing studies, and among LSRs with published results, 58.5% used the Grading of Recommendations, Assessment, Development and Evaluation system. The proportion of LSRs with a centralized platform for sharing results was higher among (i) those that included updates, (ii) Cochrane reviews, (iii) non-COVID-19 LSRs, and (iv) funded LSRs. Few LSRs included interactive features.

The number of LSRs is growing at an accelerating rate, but this survey illustrates that there are still methodological limitations and challenges that carefully need addressing. Key areas for improvement include more explicit prespecified updating strategies and better use of web-based platforms for disseminating results.

Every year, a huge amount of health-related research is published and it is difficult for busy doctors and health care workers to keep up to date with all of the new evidence. To help with this, the research can be summarized by carrying out a review. This is known as a "systematic review" if it is carefully carried out by two or more researchers. We use systematic reviews to get an accurate and fair summary of all the research available. However, these reviews can take a long time to create and can quickly become out-of-date. There is a new and exciting type of review called a "LSR" which is continually updated with new research evidence as it becomes available. This type of review is hugely important for "high-priority" health questions that need to be put into practice straight away, such as new treatments for COVID-19. As LSRs have become more popular since the COVID-19 pandemic, it is important to understand how LSRs are actually being performed and how well they share their results. In 2021, a group of researchers collected all the health-related LSRs that exist. In March 2023, we aimed to collect any new LSRs since then, and summarize what they look like now. Including LSRs found by the previous group, we found 168 LSRs, where 92 were found since May 2021. There now exist more COVID-19-related LSRs than non-COVID-19-related ones, but both groups are increasing in popularity. How LSRs decided when to "update" their results varied a lot. Non-COVID-19-related LSRs and those that had funding were more likely to use online tools to share their results, but very few used tools to let readers interact with the results. By looking at how LSRs are performed, we have shown that there are still challenges that need more work. Key areas for improvement include creating better ways on deciding when and how these reviews should be updated, and building tools to help researchers summarize the findings in a way that is reliable and easily understandable to everyone involved, including patients.