Objectives: To examine changes in completeness of reporting and frequency of sharing review materials in systematic reviews (SRs) over time; and factors associated with these changes.
Methods: We examined a random sample of 300 SRs with meta-analysis indexed in PubMed, Science Citation Index, Social Sciences Citation Index, Scopus and Education Collection in November 2020. We compared the extent of complete reporting in these reviews against 110 SRs indexed in MEDLINE in February 2014. We examined associations between completeness of reporting and various factors (e.g. self-reported use of reporting guidelines, journal’s data sharing policies) by calculating risk ratios (RR) and 95% confidence intervals (CI).
Results: Among 300 SRs from 2020, authors of only 7% shared their review data file(s) and 1% shared analytic code. Compared to 2014 sample, reviews in 2020 were more likely to reference reporting guidelines in their manuscript (RR=2.8, 95% CI 2.1-3.8), report the full search strategy for at least one database (RR=1.3, 95% CI 1.1-1.6) and methods of data preparation for meta-analysis (RR=2.2, 95% CI 1.4-3.5). Among reviews in 2020, those for which authors mentioned using reporting guidelines reported review protocols, study screening processes and numbers of records retrieved for each database more frequently than those that did not mention reporting guidelines; however the 95% CIs for these associations included the null. Reviews published in journals that mandated either data sharing or inclusion of Data Availability Statements were more likely to share their review materials (e.g. data, code files) (RR=8.1, 95% CI 3.1-21.5).
Conclusion: There was a notable increase over time in self-reported use of a reporting guideline, but we were uncertain whether it was associated with improved reporting of SRs. Data sharing policies of journals potentially encourage sharing of review materials. Further studies are needed to explore other facilitators or barriers to complete reporting in SRs.