People who live in U.S. counties where automobile assembly plants close are much more likely to die of opioid overdoses than the general public, according to a study published on the JAMA network.

Researchers compared data between counties with automotive plants that were closed between 1999 and 2016 with those that remained open. Automotive assembly plant closures were associated with a statistically significant increase in county-level opioid overdose mortality rates among adults aged 18 to 65 years.

Those results, according to study authors Atheendar S. Venkataramani, MD, PhD; Elizabeth F. Bair, MS; Rourke L. O’Brien, PhD and Alexander C. Tsai, MD, PhD, highlight the potential importance of the role of declining economic opportunity in the US opioid overdose crisis.

“Fading economic opportunity has been hypothesized to be an important factor associated with the US opioid overdose crisis,” according to the study. “Automotive assembly plant closures are culturally significant events that substantially erode local economic opportunities.”

Some 112 “manufacturing counties” primarily in the South and Midwest with at least one operational auto assembly plant were used in the analysis. The researchers compared opioid overdose mortality rates before vs after automotive assembly plant closures in counties affected by plant closures compared with changes in manufacturing counties. Five years after a plant closure, mortality rates had increased by 8.6 opioid overdose deaths per 100 000 individuals in exposed counties compared with unexposed counties, an 85% increase relative to the mortality rate of 12 deaths per 100 000 observed in unexposed counties at the same time point.

The researchers observed similar patterns of prescription vs illicit drug overdose mortality.

The United States has experienced a sharp increase in fatal opioid overdoses over the last two decades. While policy changes have tried to address factors like physician prescribing behavior and the increasing availability of synthetic opioids, “the coincident increase in opioid overdose mortality during a time of worsening economic opportunity has also sparked interest in understanding the growing demand for opioids,” say the study’s authors.

Click here to access the study, Association between Automotive Assembly Plant Closures and Opioid Overdose Mortality in the United States - A Difference-in-Differences Analysis.