Examining Opioid Overdose Risk in the Context of Changing Patterns of Opioid Prescribing and Overdose

Opioid overdose mortality continues to rise, but major shifts have occurred in the relative proportion of deaths attributed to specific opioid types. Opioids can be categorized into natural/semisynthetic opioids (e.g. including prescribed hydrocodone and oxycodone), heroin, synthetic opioids besides methadone (e.g. fentanyl, often illicit) and methadone. Overdoses in the prior decade were primarily due to natural/semisynthetic opioids from prescribed sources. Recently, overdoses from heroin and synthetic opioids, from illicit sources, have risen. Heroin overdoses increased by 33% per year from 2010-2014 and in 2015 and 2016 (latest data) exceeded deaths from natural/semisynthetic opioids.

Despite these dramatic changes in opioids involved in overdose, existing models of risk are based on data that predate shifts and fail to capture risk factors for heroin and synthetic opioid overdoses, which may differ from those associated with prescription opioid overdose. Per the CDC’s 2017 Annual Surveillance Report of Drug-Related Risks and Outcomes, examining recent data is needed “to address a diverse and evolving array of drug types.” In response to policies trying to reduce overdose risk, opioid prescribing has decreased substantially since 2012 and high dosage opioid prescribing (daily dosage ≥90 MME) in particular declined by 41.4% from 2010 to 2015. Yet, overdoses continue to rise. Given the uncertainty about why prescribing changes have not resulted in concurrent decreases in overdose rates, it is critical to understand the impacts of opioid reduction measures on overdose rates across the specific types of opioids involved.

To examine risk factors and impacts of opioid reduction on opioid overdose, we will analyze 2012-2016 VHA data. Outcomes are unintentional opioid overdose deaths categorized by opioids involved: natural/semisynthetic, heroin, synthetic besides methadone and methadone.

Aim 1: Examine opioid receipt and other patient-level risk factors associated with unintentional opioid overdose for each of the four categories of opioids involved in overdose.
Hypothesis 1: Risk factors will differ between different types of opioids involved; e.g. higher prescribed opioid dosage will be associated with natural/semisynthetic opioid overdose, but not with other categories.

Aim 2: Examine the relationship between changes in opioid prescribing within VHA facilities and overdose death rates for each of the four types of opioids involved in overdose.

Hypothesis 2: Larger reductions in opioid prescribing will be associated with reductions in natural/semi-synthetic overdoses but not with reductions in heroin and synthetic opioid overdoses.
Findings will be summarized on risk factors for overdose and impact of opioid reduction policies on overdoses across the four types of opioids and disseminated via the Outreach and Translation Core. This work has high potential to improve efforts nationally to prevent opioid overdose across the spectrum of opioids involved by helping to adapt thinking about overdose risk in the setting of changing overdose trends. Results would help inform how to screen for overdose risk and a detailed understanding of the relationship between facility-level reductions in opioid prescribing and overdose risk will inform whether additional overdose prevention efforts should be implemented alongside interventions to reduce opioid prescribing.