How Is Scale Incorporated Into the Economic Evaluation of Interventions to Prevent Obesity or to Improve Obesity-Related Risk Factors: A Systematic Scoping Review.

Introduction: Obesity prevention interventions commonly need to be implemented at scale, to address what is a significant population-level issue. While systematic reviews on the economic evidence for interventions preventing obesity or reducing obesity-related risk factors exist, to date there has been no empirical focus on the methods used to quantify the impacts of scale on intervention cost-effectiveness. This systematic scoping review aimed to synthesize the methods used to incorporate scale considerations and provide future directions for incorporating scale into economic evaluation of public health interventions.

Methods: A systematic search was undertaken by two reviewers using six databases in June 2023 to identify published economic evaluations of obesity prevention interventions, from which primary studies that quantitatively incorporated scale into their analyses were identified and included. Narrative synthesis of methods used to incorporate scale considerations.

Results: Fifty-one relevant primary studies were identified, comprising five within-trial and 46 modeled economic evaluations of 132 discrete interventions. Within-trial economic evaluations commonly estimated intervention cost assuming scale, and generally used simplistic methods and assumptions to do so. Only three modeled economic evaluations of interventions actually implemented at scale were identified. The methods used to estimate scale impacts on costs, effects, and populations exposed to interventions were heterogeneous, with few studies including equity-informed analyses.

Conclusions: More guidance is needed on how to appropriately incorporate scale into economic evaluations, whether conducted within-trial or using modeling approaches. This is especially important due to the necessity of population-level interventions to address major health issues like obesity.