(CNN) – Firearm deaths surged in the US during the Covid-19 pandemic, killing a record number of people in 2021. But as America's gun epidemic gets worse, its burden is not equal.

A new study published Tuesday in JAMA Network Open analyzed firearm deaths over the past three decades -- a total of more than 1 million lives lost since 1990. The researchers found that firearm mortality rates increased for most demographic groups in recent years -- especially during the pandemic -- and vast disparities persisted.

While recent data shows some familiar patterns, the sheer scale of the issue brings the United States to a "new moment in the history of firearm fatalities," said Dr. Eric Fleegler, a pediatric emergency physician and researcher with Boston Children's Hospital and Harvard Medical School and co-author of the study.

"At this moment in time, we have seen a dramatic increase that is really unparalleled," he said. "During the time of the Covid pandemic, going from 2019 up to 2021, we've seen over a 25% increase in fatalities in two years alone. That has never happened."

Overall, men are significantly more at risk. Nearly 86% of all firearm deaths since 1990 have been among men, according to the study, which used data from the US Centers for Disease Control and Prevention. The researchers found that firearm homicides were highest among Black men, and firearm suicide rates were highest among senior White men.

Rates of firearm homicide for both men and women nearly doubled between 2014 and 2021, but men were still more than five times more likely to die than women. Rates of firearm suicide were also seven times higher among men than women in 2021, despite increasing suicide rates among women over time.

The racial disparities are even starker. The homicide rate among young Black men -- 142 homicide deaths for every 100,000 Black men ages 20 to 24 -- was nearly 10 times higher than the overall firearm death rate in the US in 2021.

Homicide rates among Black and Hispanic men were highest in the 20 to 24 age group. But for White men, the rate was highest in the 30 to 34 age group. When comparing these groups, the homicide rate was nearly four times higher among young Hispanic men compared with White men, and the homicide rate among young Black men was a staggering 22 times higher than among White men.

"When we think about bad disparities, we're often thinking about a 20% increase, or a 50% increase. With infant mortality in the United States, when you look at Black infants versus White infants, there's over a two-fold (difference in) mortality rate. And that is a huge number to think about," Fleegler said. "And here we're talking over 20-fold. These are orders of magnitude differences that are just worsening. And they demand that type of attention."

A county-level analysis showed that firearm mortality shifted from the West to the South over time, as firearm homicide rates remained concentrated and growing in the South and firearm suicide rates spread more evenly across the country.

Urban areas had a higher burden of firearm mortality than rural areas, too.

There are two key factors driving community gun violence, says Jonathan Jay, an assistant professor at Boston University School of Public Health: disadvantage at the neighborhood level and exposure to gun violence at the individual level.

"Gun violence is most likely in spaces that show signs of physical disinvestment. Sometimes that looks like unkempt, vacant lots or abandoned houses that are boarded up, maybe a high density of liquor stores and a low density of healthy food options," he said.

For Jay, who received a grant from the National Institutes of Health to study the racial disparities in gun injuries among US youth, it's not surprising that patterns in firearm fatality rates only got worse -- because the pandemic only exacerbated existing disparities.

"It makes sense that the worst early impacts would be in neighborhoods that faced the highest disadvantage and impacts of segregation before the pandemic," he said. "Some people have talked about it like a mystery as to why gun violence would stay high even as things change in the pandemic. I think one possible explanation is just that things -- social conditions -- haven't changed that much."

But also, the pandemic exposed people to lots of things that made them feel unsafe and may have made individuals more likely to feel like they needed to carry a weapon for protection, he said.

Mental health challenges grew throughout the pandemic and violence increased, but a separate analysis from researchers at Johns Hopkins University found that guns made those things significantly more deadly. Between 2019 and 2021, all of the increase in suicides and most of the increase in homicides was due to guns. The gun suicide rate increased 10% while the non-gun suicide rate decreased by 8%, and the gun homicide rate increased 45% while the non-gun homicide rate increased only 6%.

"What we've seen is that the economic and social stressors during Covid have exacerbated health disparities across the spectrum," said Ari Davis, a policy adviser at the Johns Hopkins Bloomberg School of Public Health Center for Gun Violence Solutions.

"The same, same stressors -- social isolation, cutting social services and support -- are risk factors for violence. I think all those things contributed to a rise across the board, but disproportionately burdening those who are most vulnerable."

The research published in Tuesday "confirmed much of what we already know," researchers from the University of Michigan wrote in a related editorial -- there's a broad gender difference, an urban-rural divide, and racial disparities in firearm mortality rates in the US.

"This burden is not distributed equally, and recent increases in firearm mortality rates are most pronounced among the demographic groups and regions that were already among the most affected," they wrote.

But the analysis helps identify high-risk groups that can benefit most from targeted interventions.

Dr. Christopher Rees, an emergency department physician at Children's Healthcare of Atlanta, researcher at Emory University School of Medicine and co-author of the study, moved from Boston to Atlanta a little over a year ago. He said he's cared for "far more" children who have been injured from firearms in Atlanta than he did in Boston -- living out the trends he found in his research.

"Every single time I just think, 'One, this is awful. Two, this is someone's kid.' And I immediately think about my two children at home. And then three, I think, 'This didn't have to happen, especially to a child,' " he said. "It is very personal each time."

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