Project Summary The opioid crisis in the United States has reached a critical stage, with unprecedented levels of illness and death. In 2021, over 106,000 individuals died from drug overdoses, with opioids contributing to more than 80,000 of these deaths, accounting for 75% of all drug-related fatalities. Ohio has been particularly affected, ranking fourth nationally in overdose death rates in 2019, and experiencing a shocking 1000% increase in opioid-related deaths in Cuyahoga County from 2007 to 2016. By 2021, Ohio reported an opioid-related death rate of 48.1 per 100,000 residents, significantly higher than the national average, and saw a notable surge in opioid overdoses during the COVID-19 pandemic. Alongside the loss of life, Ohio faces increased risks of Hepatitis C and HIV epidemics due to opioid misuse. Certain demographics, including the unemployed, homeless, those with lower education levels, lacking social support and health insurance, and individuals in the legal system, are disproportionately affected by opioid overdoses. Despite concerted efforts and dedicated resources to combat opioid use disorder (OUD), a major challenge in addressing Ohio's opioid crisis remains the lack of reliable estimates of OUD prevalence. This proposed study extends the work of the Opioid and Substance Use Disorder Data Enclave (O-SUDDEn) project, which aims to improve overdose mortality prediction by linking data. Building on this framework, the supplement will develop a model to estimate opioid use disorder (OUD) prevalence in Ohio more accurately. This data integration will enhance existing predictive models and inform targeted public health policies to address the opioid crisis. The study's central hypothesis is that by refining prevalence estimation to reflect OUD patterns and associated risk factors, evidence-based strategies and interventions can be implemented to reduce opioid-related fatalities and improve public health outcomes in Ohio. The study aims to achieve the following objectives: Aim 1: Develop and Validate a Capture- Recapture Approach Based on a Heterogeneity Model to Estimate the Prevalence of Opioid Use Disorder (OUD). This involves creating a model that integrates observed and unobserved variations in opioid-related outcomes to estimate the prevalence of OUD at the county level in Ohio. Aim 2: Assess the Impact of Demographic and Socioeconomic Factors on the Estimated Prevalence of OUD. This aim aims to use the refined prevalence estimates from Aim 1 to analyze how demographic and socioeconomic factors influence the distribution of OUD across different geographical areas and populations.

Public Health Relevance Statement The study's public health relevance lies in addressing the critical stage of the opioid crisis, characterized by staggering levels of illness and mortality, particularly prevalent in Ohio. By extending the O-SUDDEn project, it aims to develop a more accurate model for estimating opioid use disorder (OUD) prevalence, which can enhance existing predictive models and guide targeted public health interventions to mitigate opioid-related fatalities and improve overall health outcomes in Ohio.