Reporting according to the preferred reporting items for systematic reviews and meta-analyses for abstracts (PRISMA-A) depends on abstract length

To evaluate reporting of abstracts of systematic reviews according to the preferred reporting items for systematic reviews and meta-analyses for abstracts (PRISMA-A) 2013 checklist.A random sample of 534 systematic reviews on effectiveness indexed in PubMed between 2000 and 2019 was assessed. Adherence of abstracts to PRISMA-A was analysed using descriptive statistics. Results were stratified by number of words, structure, and year of publication.The mean score of fully reported PRISMA-A items was 5.4 of 12, with adherence varying widely between items (0% to 98.8%). Cochrane reviews received higher mean total scores than non-Cochrane reviews (6.3 vs. 5.2). Adherence to PRISMA-A increased linearly with increasing word count. In non-Cochrane reviews, authors of structured abstracts more often adhered to PRISMA-A than those of unstructured abstracts. No improvements in reporting of abstracts were found after the implementation of PRISMA-A in 2013.Adherence to PRISMA-A shows great potential for improvement. Therefore, authors, editors, and reviewers should be made aware of PRISMA-A by referring to it in the journal submission guidelines. As adherence to PRISMA-A increases with the number of words, journals should consider to increase the word limit to 250-300 words.