The phrase “leading causes of death” might bring to mind cancer, heart disease, suicide and drug overdose. But new research published this month in the Proceedings of the National Academy of Sciences finds that young American men are at a surprisingly high risk of being killed by a police officer.

Among men of all races, ages 25 to 29, police killings are the sixth-leading cause of death, said a study led by Frank Edwards of Rutgers University, with a total annual mortality risk of 1.8 deaths per 100,000 people. Accidental death, which includes automotive accidents and drug overdoses, was the biggest cause at 76.6 deaths per 100,000, and followed by suicide (26.7), other homicides (22.0), heart disease (7.0), and cancer (6.3).

The data do not differentiate between police killings that were later determined to be justified and those that were not. FBI data, which are widely acknowledged to be incomplete, show that 400 to 500 homicides each year are determined to be justified, which is defined as “the killing of a felon by a law enforcement officer in the line of duty.” Those deaths represent about half of the roughly 1,000 annual police killings that independent tallies have found.

For a black man, the risk of being killed by a police officer is about 2.5 times higher than that of a white man. “Our models predict that about 1 in 1,000 black men and boys will be killed by police over the life course,” the authors wrote.

In the 20 to 24 age group, black men represent nearly 2 percent of such deaths, compared with 0.5 percent for whites. A 40-year-old black man has about the same risk of being killed by a police officer as a 20-year-old white man.

Because no reliable federal data exist for police killings, the authors turned to data compiled by Fatal Encounters, a project that uses news reports, public records requests and crowdsourced information to tally officer-involved fatalities. The authors note that Fatal Encounters was “endorsed as a sound source of data” by the federal Bureau of Justice Statistics in a 2016 report, but they warned that the data likely undercount the number of officer-involved killings: “If any death is not covered by news organizations or is not documented in searchable public records,” they note, “it will not appear in the data.”

Police killings are far more common in the United States than in other advanced democracies. That’s partly because the U.S. has a much higher homicide rate — “25.2 times higher” — than economically similar countries, according to a 2016 study. One of the prime drivers of that difference, research shows, is the nation’s high rate of gun ownership: Americans make up 4% of the global population, but own nearly half the world’s guns.

The high rates of violence and gun ownership make many police fearful for their lives, research shows. Data compiled by the National Law Enforcement Officers Memorial Fund show that, in recent years, 100 to 200 officers are killed annually in the line of duty. And other research shows that police are more likely to be killed in the line of duty in states with more permissive gun laws.

More than half of the 544 people shot and killed by police to date in 2019 were carrying firearms, said data compiled by the Washington Post. At least 20% fatally shot by police this year had documented mental health issues, according to the Post’s data.

The study’s authors say their findings reinforce calls “to treat police violence as a public health issue.”