(CNN) An automotive assembly plant closing in a US county has been associated with 85% higher opioid overdose death rates among working-age adults in that county after five years, according to a study published in the medical journal JAMA Internal Medicine on Monday.

"Relative to the trends in manufacturing counties where an automotive plant did not close, having a plant closure meant that your opioid overdose death rate was 85% higher after five years than it otherwise would have been -- and that was a large number to us," said Dr. Atheendar Venkataramani, assistant professor at the University of Pennsylvania Perelman School of Medicine , who was first author of the study.

"The study is important because it shows that when economic opportunities collapse, it not only has consequences for people's economic wellbeing but it might adversely affect their health too," Venkataramani said. "Economic opportunity matters for our health, and as the forces that are shifting economic opportunities for people are continuing to evolve, we have to think about how policies can both make people resilient -- from a health sense -- to the negative changes that might happen, and we also have to think about what types of policies on the economic side may actually give people opportunities, which may also bolster their health."

The study involved a database of automotive assembly plants in operation as of 1999, which researchers built using data from industry trade publications, automotive company websites and newspaper articles.

The researchers took a close look at the location of each plant and dates of closure. They examined the database at the county level and identified 112 manufacturing counties where the percentages of employed residents working in manufacturing were in the top quintile nationwide. The counties were primarily in the Midwest and the South. Twenty-nine of the 112 counties had closures between 1999 and 2016.