More than two thirds of gunshot victims admitted to American hospitals are covered by Medicaid, or don’t have health insurance at all. And the price of that care is staggering: The average annual cost per admission for a firearm assault injury is $20,989, more than twice that of a typical hospital stay.

These findings anchor one of the most comprehensive studies of the cost of gunshot hospitalization in the United States to date, an examination of 336,785 hospital admissions by public-health researchers at the University of Iowa, published in the July edition of the journal Injury Epidemiology. The research shows that African-American men are disproportionately represented among gun-injury admissions. It also shows the extent to which hospitals rely on government-backed insurance to pay the costs of caring for shot patients.

In the 10-year period examined by the researchers, uninsured patients and those with Medicaid or Medicare accounted for about 65 percent of the total cost of firearm-related hospital stays. Gunshot wounds resulted in an average annual cost of $622 million — a figure that the researchers say is almost certainly a big undercount, given that the estimated total population of gunshot victims is about three times the pool of patients whose data they were able to obtain.

The total annual cost for gunshot patients reliant on Medicaid alone amounted to $205 million.

“It’s important to recognize that this is a public cost,” said Corinne Peek-Asa, the study’s lead author and director of the University of Iowa Injury Prevention Research Center. “Being admitted for a firearm injury is very expensive, and we see so much of that cost is from uninsured or Medicaid sources. Which, for hospitals that see a high volume of firearm injuries, is going to be a challenge.”

Roughly 80,000 Americans survive a gunshot injury each year. While there is no official count of the number of gunshot survivors currently covered by Medicaid, Kaiser Health News reported in 2016 that thousands of gunshot survivors gained coverage after the 2014 expansion of the Affordable Care Act.

To analyze total expenditures, researchers examined data from the National Inpatient Sample (NIS), a massive database of hospital stays maintained by the federal Healthcare Cost and Utilization Project. Firearm-related admissions were identified through E codes, a way for hospitals to record and classify injuries with external causes. The researchers then converted the charge data for each admission, which indicates the price per visit charged by individual hospitals, to average costs, adjusting for the level of inflation in 2013.

Assaults were the cause for roughly 60 percent of overall injuries — with average annual costs of more than $389 million — followed by unintentional firearm injuries, which accounted for 22.6 percent of admissions and more than $117 million in annual costs. Self-inflicted firearm injuries accounted for 8.6 percent of all injuries, and more than $64 million annually.

Costs for Medicaid and Medicare patients tended to outstrip those for the privately insured. The average annual cost per visit for a Medicaid patient was $24,714, according to the study, while patients under private or HMO plans paid $19,772. Medicare patients paid an average $21,834. For comparison, the average cost per hospital stay was $10,400, according to 2012 research cited in the study.

The researchers also examined firearm injury by demographic. According to the study, nearly 50 percent of all hospitalizations were among the black population, while Hispanic patients accounted for roughly 17 percent. Blacks also had the highest rate of gun-injury admissions, at 39.7 per 100,000, compared to 4.4 among whites.

Although the NIS is the most representative hospitalization-data source, it is not designed to surveil firearm injuries specifically. It only counts hospital admissions, not treatment in emergency rooms, where a large number of firearms injuries are also treated.

Peek-Asa said she plans to keep investigating the social and economic costs of firearm-related injuries. Highlighting public costs is also one way to emphasize where treatment and prevention strategies could be most useful.

“Physical recovery is good, but I think we still need to do more work in psychological recovery,” Peek-Asa said. “And I also think we need to think way upstream at primary prevention. When a person is at the hospital and already injured, then some interventions could help them recover. But how do we prevent people from being shot in the first place?”