In a study published in the journal The Lancet Regional Health — Americas, epidemiologists at the University of Cincinnati tracked the epicenter of this life-shattering epidemic over space and time across the country, driven largely by a move from prescription opiates to heroin to synthetic substances like fentanyl.

Researchers say this geographic shift can be narrowed between 2013 and 2016 as lawmakers implemented stricter regulations limiting access to opioids and law enforcement began prosecuting doctors for allegedly prescribing them irresponsibly.

In the absence of a legal remedy, many people with substance use disorder began turning to illicit drugs such as heroin and fentanyl, UC College of Arts and Sciences Professor Diego Cuadros said.

“The key message is this is an evolving epidemic,” Cuadros said.

Researchers in UC’s Digital Epidemiology Lab discovered that the populations affected by substance use disorder also changed over the course of the deadly epidemic from homogeneously White populations to populations that now include many Black victims. Meanwhile, the substance of choice has shifted from prescription opioids to heroin and now synthetic opioids, the study found.

“Between 2013 and 2016, Black communities started having access to these synthetic opiates. And those communities have been more affected, particularly by fentanyl,” Cuadros said.

Drug overdoses are the leading cause of death for Americans ages 18 to 44, according to the Centers for Disease Control and Prevention, which provided mortality stats for the study.

“As the supply and demand dynamic of the substance evolved, so, too, did the vulnerable populations,” lead author and UC graduate Santiago Escobar said. “The type of substances being abused, as well as the means used to access them, were key determinants of which populations suffered a higher mortality.”

Study co-author Neil McKinnon, president of Central Michigan University, noted the benefits of tracking an epidemic over time.

“The epidemic is really a series of mini-epidemics, which we identify as hotspots, across rural and urban America,” he said. “We hope our results will assist those in addressing the opioid crisis.”

The research team has been studying the opioid epidemic for much of the past decade. In 2018 they identified hot spots where the opioid epidemic was having a disproportionate effect in Ohio. Subsequently, they identified similar trends nationwide in 2021 using county data to find 25 clusters where the rates of fatal drug overdoses were highest.

And then Cuadros and his students turned their attention to the COVID-19 pandemic.

“Epidemics like HIV are stable. We don’t see changes in hotspots. But for COVID, we saw different variants like delta and omicron crop up,” he said.

Those variants had a disproportionate effect both in cases of infections and deaths across the United States, he said.

“We have a similar situation here with substance use disorder,” Cuadros said. “We’re facing an epidemic that is very complex and dynamic and evolves over time.”