Background: Quasi-experimental methods (QEMs) are a family of techniques used to estimate causal relationships when randomized controlled trials are unfeasible or unethical. They offer a powerful alternative to observational studies by introducing random assignment of individuals or groups into their design, thereby offering stronger means of establishing causation. The use of QEMs in cardiovascular research has not been systematically examined to determine steps toward improving and expanding their use.
Methods: We identified 4 main techniques using a systematic search strategy from 2016 to 2021: instrumental variable analysis, interrupted time series analysis, difference-in-differences analysis, and regression discontinuity designs. QEMs are examined as alternatives to randomized controlled trials and traditional observational studies; as more observational data becomes available to researchers, there are more opportunities to apply these techniques. Eligible articles were selected based on publication in high-ranked journals. The quality of eligible articles was appraised using the Joanna Briggs Institute checklist for quasi-experimental studies.
Results: Data from 380 studies were extracted based on our inclusion criteria. Forty-two of these studies were published in the top 10 medical or top 20 cardiovascular disease journals, and 25 studies were included after quality appraisal. The review identifies the main features and limitations associated with each technique, providing readers with practical guidance on how to apply these to their research. A graphical decision aid was developed to facilitate the routine use of QEMs.
Conclusions: The use of QEMs in cardiovascular research published in contemporary, high-impact articles was examined. Findings are biased toward this segment of literature, which represents the latest developments in this growing area of cardiovascular research. The decision aid is a novel schematic that researchers can adopt into practice.
Keywords: cardiovascular research; causal inference; death; health economics; health policy; natural experiments; quasi-experimental methods.