Abstracts of Cochrane reviews are getting longer, but this has no large impact on the reporting quality.
2Faculty of Health Sciences Brandenburg, Brandenburg Medical School Theodor Fontane, Institute for Health Services and Health System Research, Rüdersdorf, Germany
In our previous study on the reporting quality of abstracts according to PRISMA-A, we found that abstracts of Cochrane reviews (CRs) were better reported than non-Cochrane reviews, differed significantly in length (median length: 507 words vs. 249 words), and appeared to be getting longer in recent years. However, the considered sample of CRs was too small to draw robust conclusions. Overall, there is a general lack of studies that address the quality of reporting or trends in the length of the abstracts of CRs.
Objectives: To evaluate the reporting of abstracts of CRs according to PRISMA-A and to investigate the possible influence of the abstract´s length.
Methods: This was a retrospective, observational study based on all CRs indexed in Medline (via PubMed) until November 18th, 2022. Trend analyses were performed on the number of publications and length of abstracts over the years for all 15,188 abstracts. Then, PRISMA-A adherence was assessed by two independent reviewers for a random sample of a planned sample size of 440 abstracts. Results were stratified by the number of words and year of publication.
Results: Overall, the median number of words in the abstract was 469 (IQR: 389-686 words), steadily increasing from 353 words in 2000 to 807 words in 2021, with less than 1% of the abstracts being less than or equal to 300 words (in 2000: 30.7%). Analyses on PRISMA-A adherence show a mean score of 6.1 fully reported items. Stratified by year, PRISMA-A adherence increases with increasing word count in 2000-2010 and 2011-2015, whereas there is no difference in PRISMA-A adherence by the abstract length in 2016-2022.
Conclusions: Over the years, abstracts of CRs have become longer and longer, running up to 1,000 words. This conflicts with the Cochrane Handbook, which recommends a maximum length of 400 words before being adapted to MECIR in 2019, which has recommended a length of less than 700 words since 2012 but allows a length of up to 1,000 words. It is questionable whether such long abstracts meet the goal of presenting all essential contents of the article in an informative, accurate, appealing, and concise form. Patient, public, and/or healthcare consumer involvement: No involvement.