The life and death of living systematic reviews: a methodological survey

The objectives of this study are to describe the characteristics of living systematic reviews (LSRs) and to understand their life cycles.

We conducted a comprehensive search up to April 2021 then selected articles and abstracted data in duplicate and independently. We undertook descriptive analyses and calculated delay in version update and delay since the last published version.

We included 76 eligible LSRs with a total of 279 eligible versions. The majority of LSRs was from the clinical field (70%), was COVID-19 related (63%), and had a funding source specified (62%). The median number of versions per LSR was 2 (interquartile range (IQR) 1-4; range 1-19). The median and IQR for the ratio of the actual period of update to the planned period of update was 1.12 (0.81; 1.71). Out of all reviews with a 'planned period of update' and at least one update (N = 19), eight LSRs (42%) had a period since last published version greater than 3 times the planned period of update. No LSR included a 'retirement notice' in their latest published version.

While most LSR complied with the planned period of producing updates, a substantive proportion lagged since their last update.