Evaluating the Public Health Impact of Interventions for the Prevention of Drug-related Deaths in the Population: in Scotland [EPHESUS]

Background

Drug-related mortality is a public health crisis in the UK; drug-related deaths (DRD) in Scotland have doubled in last decade. Opioid agonist therapy (OAT) reduces DRD risk by over 50%. Periods of elevated mortality risk when starting and leaving OAT combined with poor retention, as well as increased risk associated with poly-drug use (especially with street benzodiazepines (BZD)), may reduce population benefits of OAT.

New long-acting formulations of OAT (la-bup) could increase retention and so improve effectiveness. Since 2011, Scotland’s National Naloxone program (NNP) has distributed >150,000 naloxone kits, which can be administered after someone uses opioids to prevent fatal overdose. Plans for safer drug consumption facilities (SDCF) and safer BZD prescribing will be piloted during our study.

Aim To evaluate the population-level impact of existing and novel interventions for reducing DRD in Scotland. Methods

Objective 1: We will analyse the Scottish Public Health Drug Linkage Programme to determine: DRD mortality rates at critical risk periods in and out of OAT; individual and programmatic factors associated with OAT retention and time to re-engagement; if DRD risk changed during COVID-19; if OAT retention and outcomes improved after implementation of new drug treatment standards; impact of OAT on re-incarceration and DRD after prison release; effectiveness of la-Bup. An individual-based model of OAT and DRD among people with opioid dependence will be developed, parameterised and calibrated primarily using the linked data. The model will be used to evaluate how many DRD have been averted by OAT as delivered in Scotland.

Objective 2: The model will be extended to include non-fatal overdoses and naloxone distribution. The model will be parameterised and calibrated using NNP data, data on ambulance callouts for overdoses and survey estimates of the prevalence of non-fatal overdose among people who inject opioids. The model will estimate the additional number of DRD averted by NNP. We will estimate costs of the NNP and incorporate these into the model to estimate NNP cost-effectiveness.

Objective 3: Projecting forwards, the model will be used to evaluate how changes to OAT delivery could increase the impact of these interventions. Finally, the model will be extended to evaluate the potential impact of introducing novel interventions, including SDCFs and BZD safer prescribing, and consider the impact and costs of alternative DRD prevention strategies as proposed by our stakeholders.

Throughout, people with lived experience and other stakeholders will advise on project priorities, model scenarios for objective 3, interpretation and implications of the research findings. Timelines for delivery

Model findings for objective 1 will be available in Year 1-2; objective 2 in Year 2-3, and objective 3 during Years 3 and 4. Anticipated impact & Dissemination

Our key aim is to improve the evidence on what actions can be taken to reduce DRD in the population, informing changes to drug policy and public health guidance in UK and internationally. Through Co-Is and stakeholder meetings, findings will be shared with Scottish Government, drug treatment providers in Scotland and England, public health director leads and other stakeholders.

Model code and dummy data sets will be available. Lay summaries and infographics of key outputs will be coproduced with our PPI advisory group, Scottish Drugs Forum and Policy Bristol.