A systematic review of stepped wedge cluster randomized trials in high impact journals: assessing the design, rationale, and analysis

Objectives: Stepped wedge cluster randomized trials (SW-CRTs) are an appealing study design because they enable sequential roll out of an intervention across clusters, bringing logistical advantages. This review aimed to evaluate the design rationale, design features, stepped wedge diagram, and analytical approaches of SW-CRTs published in high-impact medical journals from 2020 to 2023, focusing particularly on adherence to key guidelines from the Consolidated Standards of Reporting Trials extension to SW-CRTs.

Study design and setting: We conducted searches across PubMed and Cochrane Central Registry of Controlled Trials databases for SW-CRTs published between January 2020 and December 2023 in eight high-impact journals. Eligibility criteria included peer-reviewed publications of randomized SW-CRTs involving human participants, published in English.

Results: Of the 23 SW-CRTs included in the review, 70% had "stepped wedge" explicitly mentioned in their titles. Most studies (96%) included a stepped wedge diagram, but only 65% of these diagrams clearly communicated the duration of each time period. There was considerable variability in design features, including number of sequences (median of 7, range 3-20) and clusters (median of 15, range 9-19). The majority of trials (78%) provided robust justifications for selecting a SW-CRT design, for example, citing practical or logistical constraints. However, 22% of the studies offered less convincing rationales. Generalized linear mixed models were the most frequent analysis method employed.

Conclusion: Our review has highlighted areas for improvement in the presentation of SW-CRTs, particularly in clearly indicating the duration of time periods within diagrams and providing robust justifications for selecting a SW-CRT design.

Plain language summary: The stepped wedge cluster randomized trial (SW-CRT) is a type of study design that introduces interventions to different groups at different times. This review examined reports of SW-CRTs published in top medical journals from 2020 to 2023 to see if they followed certain guidelines such as including the word "stepped wedge" in their title. A total of 23 SW-CRTs were included in the review, with 70% mentioning "stepped wedge" in the title. Most (96%) included diagrams, but only 65% showed the duration of each time period clearly. There was variability in design, such as variations in the number of sequences and groups. 78% gave valid reasons for using SW-CRTs, citing practical benefits, whereas 22% did not give convincing reasons. This review suggests that improvements can be made in the presentation of stepped wedge diagrams and in the reporting of SW-CRTs. Researchers should clearly report the length of time periods and provide strong justifications for their design choice.