Many of America's doctors who were heroes on the frontlines of the pandemic paid the ultimate price for their efforts, a new analysis shows.

An estimated 622 extra deaths occurred among U.S. doctors aged 45 and over from the pandemic's onset in March 2020 through December 2021, researchers say.

Older doctors who provided direct care to patients battling COVID were at especially high risk.

These excess deaths to physicians didn't subside until April 2021, soon after the introduction of COVID vaccines, concluded a team led by Mathew Kiang, an epidemiologist at Stanford University's School of Medicine in California.

The findings were published Feb. 6 in the journal JAMA Internal Medicine.

The only good news coming out of the new study: Despite the tragic loss of so many doctors' lives, death rates among physicians were still lower than that observed among the general population.

That suggests "personal protective equipment use, vaccine requirements, infection prevention protocols, adequate staffing and other workplace-based protective measures were effective" in preventing more deaths among doctors, the authors wrote.

They conducted the study by comparing pre-pandemic data on deaths to older (age 45 and above) physicians from 2016 through February 2020 to data collected during the pandemic itself.

Almost 800,000 physicians were included in the analysis. The team excluded younger physicians from their analysis because deaths among that group were very low (fewer than five deaths per month).

Deaths to U.S. doctors peaked in December 2020, the study found, with 70 excess fatalities occurring that month. Deaths began to decline through 2021.

Among the 622 excess deaths recorded during the pandemic, certain factors seemed to raise the risk that a doctor might die, the study found. Men made up about two-thirds (65.3%) of those who passed away, and the odds that a doctor might die during the pandemic rose with his or her age, the report found.

Older doctors who cared for COVID patients appeared to be at especially high risk, suggesting that hospital "workplace policies should prioritize mitigating risks in this group" in the future, Kiang and colleagues wrote.

Of course, the deaths of working physicians may have exacerbated a wider tragedy: more deaths to patients, as hospitals faced staffing shortages caused (at least in part) by the loss of these valuable crew members.

That's why "preventing excess deaths among physicians is an important component of mitigating excess deaths in the general population," the study authors concluded.