Open Science Practices in Systematic Reviews From 2014 to 2024: A Cohort Study of 300 Systematic Reviews.

Objectives: Open science practices, including the preregistration of protocols and the sharing of data and code, are increasingly promoted to enhance transparency, accessibility and the reuse of research outputs. However, systematic reviews, which are essential for informing clinical guidance and policy, often provide limited access to the materials needed for independent verification and reuse. Our objective was to estimate the prevalence of key open science indicators in interventional systematic reviews and to assess temporal changes by comparing our 2024 cohort with previously published cohorts from 2014 to 2020. Design: Cross-sectional meta-research study. Data Sources: MEDLINE, Embase, and CINAHL were searched in June 2024 for English-language records indexed between 1 January and 1 February 2024. Eligibility Criteria: Interventional systematic reviews including human participants, a clearly defined PICO question, a systematic search strategy, a risk-of-bias assessment, and at least one meta-analysis. Methods: Following our publicly registered protocol and STROBE guidance, records were randomly sampled and screened in duplicate until 300 eligible reviews were included. Data extraction was conducted in duplicate. We assessed protocol registration and availability, data sharing, code sharing, and preprint dissemination. Preprints were identified through extensive manual searches across more than 40 preprint servers and through author contact. Temporal changes were examined by comparing our 2024 cohort with previously published cohorts from 2014 to 2020 using pairwise risk ratios (RRs) with predefined equivalence ranges. Results: Among the 300 included reviews, cancer was the most common health condition (17%), and pharmacological or biological interventions were the most common intervention type (35%). The median number of primary studies included in each systematic review was 14 (IQR 9-23). Most reviews (73%) were published in journals with data and/or code-sharing policies. In the 2024 cohort, 70% of systematic reviews reported a registered protocol or protocol availability and 61% included a data availability statement. However, only 24% shared underlying data, and analytical code was shared in 1% of reviews. Preprints were rare, occurring in 2% of the reviews. Reporting of protocol registration or availability increased substantially over time (2024 vs. 2014: RR 2.03, 95% CI 1.55-2.65; 2024 vs. 2020: RR 1.67, 95% CI 1.43-1.95), as did data availability statements (2024 vs. 2020: RR 1.98, 95% CI 1.63-2.40). Data sharing showed a nonlinear pattern, decreasing from 2014 to 2020 (RR 0.22, 95% CI 0.13-0.36) and increasing from 2020 to 2024 (RR 3.71, 95% CI 2.30-6.00), but remained uncommon overall. Code sharing was rare and showed no detectable change (OR 1.00, 95% CI 0.15-6.51). In the 2024 cohort, 3% of protocols were registered after manuscript submission. Conclusions: Several transparency indicators became more common over time, although trends differed across indicators. Yet the sharing of reusable research materials remains uncommon. Reusable data, analytic code, and preprints are rare outside the context of pandemics. These findings highlight a persistent gap between declarative openness and operational accessibility, emphasizing the necessity for more robust, verifiable mechanisms from journals and funders to reduce data distance and support independent verification and reuse of systematic review evidence. This gap between declared openness and practical accessibility continues to limit independent verification and reuse of systematic review evidence.