How long does it take to complete and publish an animal systematic review?

Introduction: Conducting a rigorous animal systematic review requires a priori registration of a study protocol. However, it remains unknown how many of these registered studies culminate in publication and how long it takes researchers to complete such a systematic review. Thus, the objective here was to assess the proportion of systematic review protocols which culminate in publication, including the time required to complete and publish such a study. We also evaluated demographic and quality parameters of systematic review protocols.Methods: All available animal systematic reviews protocols were manually curated from PROSPERO, the international registry of systematic review protocols. Start and completion date as well as topical and demographic data were extracted, complemented by a web-scraping approach. Assessment of publication status was achieved through a systematic literature search. Results: Out of 1365 protocols, 694 resulted in a published systematic review (51%). The top five prolific countries in terms of the number of registered protocols were Brazil (376 protocols, 28% of total protocols), China (216, 16%), The UK (94, 7%), The Netherlands (93, 7%), and the USA (92, 7%) Median time to complete and publish a systematic review was 11.5 months (range 0.13-44.9 months) and 16.2 months (range 1.0-49.7 months), respectively. This time was 69% more until submission than anticipated by the authors (6.8 months range: 0.9 – 48.0). The time from protocol submission to registration in PROSPERO was 1.1 months (range 0-17 months). Having a larger author team (≥4 authors) and a cross-country collaboration did not significantly increase the required times to complete a review. The median number of authors per review was 4 (range: 1-16).Conclusion: The majority of the systematic review protocols do not result in publication potentially indicating publication bias. And while there may be exceptions, authors can generally expect to complete an animal systematic review within less than one year. Areas which might require teaching are a priori registration of study protocols and risk of bias assessment tools.