On this page, you can find examples of previous natural experiment studies conducted in the field of emergency and (orthopedic) trauma surgery. Also, various meta-analyses from this field of research are presented, where results from randomised trials are complemented by results of natural experiments. Recent articles by members of the NEXT study group about key methodological of observational studies are listed too.
The publication policy of the NEXT study group can be found here
A common threat to the validity of observational studies of medical treatment is the impossibility to correct for inherent incomparability between the groups of patients who receive different treatments. This is referred to as confounding.
Natural experiments are observational studies where natural variation in treatment allocation is utilized to increase the validity of the results of observational studies of treatment effects. There are various example of natural experiment studies listed below. What these examples have in common is that the differences in the treatments that patients receive do not depend so much on differences in patients characteristics, but much more on for example the hospital they visit or the preferences of the doctor who treats them. Observational comparisons grounded in natural experiments are likely to be less prone to bias due to confounding.
Members of the NEXT study group advocate including observational studies in systematic reviews and meta-analyses of the effects of medical treatments. The strength of including observational studies in systematic reviews and meta-analyses is that all available evidence on a given topic is presented, including the real-world variety of study populations and long-term outcome effects. In such reviews, data of RCTs and observational studies can be presented separately which allows readers to draw their own conclusions. On top of that, for each study, the quality can be appraised using available methodology (such as the MINORS criteria, the ROBINS-I tool, or the Cochrane Risk of Bias assessment tool), to provide readers with key information to appraise the validity of the included studies (RCTs and observational).
Our research group published several systematic reviews and meta-analyses including observational data for (orthopaedic) trauma. These studies show the added value of including observational evidence: including more studies leads to larger sample sizes, which allows for more detailed investigation of subgroup effects. What is more, observational studies appear to be more representative of daily practice, e.g., in terms of patient and surgeon characteristics. Provided that the included observational studies are of sufficient quality, their results complement those of RCTs.
Below is a list of papers that describe some of the challenges of natural experiments and how to mitigate those challenges. Together with the literature cited in these papers, they could serve as a starting point to explore the vast amount of literature on this topic.