Modelling overdose case fatality rates over time: The collaborative process

This study describes the collaborative process undertaken to study trends in the overdose case fatality rate (the proportion of drug overdoses resulting in death) in Kentucky from 2018 to 2021. Rather than separately tracking counts of fatal and non-fatal overdoses, studying the overdose case fatality rate gives insight into issues related to the severity of drug overdoses and the efficacy of overdose response resources. We found that the overdose case fatality rate increased across the study period at a rate of approximately 1.19 percentage points per year, and in addition to this annual trend, it is expected to peak 1.26 percentage points higher in the wintertime and lower in the summertime than what would be expected from the overall annual trend. Modelling trends in the overdose case fatality rate over time in a way that is methodologically sound and easily interpretable to community stakeholders was a challenge, and the solution to utilize Bayesian beta regression was made possible by effective team science between domain experts and methodological experts. In this work, we describe our collaborative process, including the team structure and communication strategies, that ultimately led to these novel findings regarding seasonal and annual trends in the overdose case fatality rate.