October 14, 2021

Between 2015 and 2019, North Carolina saw an increase in overdose deaths that involved multiple drugs, according to a new article from researchers at UNC-Chapel Hill.

Kristin Shiue

Kristin Shiue

Published in Drug and Alcohol Dependence, the study was led by a team of researchers at the UNC Gillings School of Global Public Health and the UNC Injury Prevention Research Center (IPRC), including Kristin Shiue, MPH, doctoral student in epidemiology and graduate research assistant at IPRC; Anna Austin, PhD, assistant professor of maternal and child health; and Rebecca Naumann, PhD, assistant professor of epidemiology. Austin and Naumann are core faculty at IPRC. They collaborated with Scott Proescholdbell, MPH, and Mary E. Cox, MPH, from the N.C. Department of Health and Human Services Division of Public Health, and Michelle Aurelius, MD, who is N.C.’s chief medical examiner.

Dr. Becky Naumann

Dr. Becky Naumann

Dr. Anna Austin

Dr. Anna Austin

“There is an added layer of detail that can be gleaned from the literal text on death certificates, and this is frequently overlooked in overdose research,” Shiue explained. “We wanted to demonstrate the value of this data in improving overdose surveillance efforts.”

The researchers used N.C. death certificate data between 2015 and 2019 and leveraged the literal text, which is the descriptive information provided by the medical certifier of the death certificate, to analyze specific drug involvement in drug overdose deaths. Typically, research studying drug involvement in overdose fatalities uses standardized codes from the International Classification of Diseases (known as ICD-10 codes). However, ICD-10 codes alone are not enough to understand the detailed specifics of drug involvement, as the codes generally reflect broad categorizations of substances. Additionally, they can mask an understanding of the number of different drugs involved in a death from a research and surveillance perspective, if more than one drug is classified under the same broad category or class.

After systematically searching the literal text for drug mentions, the research team found that approximately three in four overdose deaths in N.C. during the timeframe of the study involved multiple drugs – known as “polydrug involvement.”  Literal text identified a greater percentage of deaths with polydrug involvement compared to ICD-10 codes alone. The substance classes most commonly involved in overdose deaths were opioids (80 percent), psychostimulants (37 percent), benzodiazepines (27 percent), alcohol (15 percent) and antiepileptics/sedative-hypnotics (15 percent).

Through analysis of the literal text, the team was able to further identify the specific drugs driving the broader substance class trends. Over this period, opioid involvement in overdose deaths shifted from heroin and prescription opioids, such as oxycodone or hydrocodone, to predominantly fentanyl, the latter of which was involved in nearly 60 percent of overdose deaths in 2019. Psychostimulant involvement increased for both cocaine (from 21 percent in 2015 to 35 percent in 2019) and methamphetamine (from three percent in 2015 to 13 percent in 2019. In 2019, nearly 80 percent of all overdose deaths involved a combination of fentanyl, cocaine, heroin and/or methamphetamine.

“This study highlights the rapidly changing nature of the overdose crisis in N.C.,” said Aurelius, “and we know that preventing these deaths will continue to take an all-hands approach between surveillance partners, researchers, public health professionals, clinicians and treatment providers, harm reduction colleagues, and advocates across the state.”

“We also wanted to develop an accessible resource, with the hope that other researchers and state partners will use and build upon our work,” said Shiue.

The researchers have shared their code for searching the literal text.

To continue research in this area, the team is currently conducting a deeper investigation into overdose deaths by intent, including examining differences in specific drug involvement between unintentional versus suicide overdose deaths.

To learn more, read the full article online.


Contact the UNC Gillings School of Global Public Health communications team at sphcomm@unc.edu.

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