Firearm-related injuries drop 20 percent during NRA conventions: Study A study in the New England Journal of Medicine sheds light on gun injuries.

 -- What would cause a 20 percent decline in firearm injuries in the U.S. during a given period of time?

According to new research published in the New England Journal of Medicine, the answer is the National Rifle Association’s annual convention.

Harvard Medical School's Anupam Jena and Columbia University's Andrew Olenski tallied both emergency room visits and hospitalizations during identical days three weeks before, three weeks after, and during NRA conventions between 2007 and 2015.

The NRA convention, which typically lasts four days, draws up to 80,000 gun enthusiasts.

Particularly striking is that local gun injuries -- those that occur in the state that the convention is held -- show a 63 percent drop during convention week.

The researchers point out that local gun ranges often close so that their workers may attend the convention, as do some hunting areas. The cities studied, from 2007 to 2015, were Nashville, Indianapolis, Houston, St. Louis, Pittsburgh, Charlotte, Phoenix and Louisville.

But a note of caution: It's not that gun-related crime decreased. The aforementioned figures pertain solely to injuries. In 2015, for example, the U.S. logged nearly 85,000 firearm injuries, of which 17,000 were unintentional.

The authors concluded that firearm-safety concerns and risks of injury are relevant, even among experienced gun owners.

"Fewer people using guns means fewer gun injuries, which in some ways is not surprising,” said Anupam Jena, senior author of the study and the Ruth L. Newhouse associate professor of Health Care Policy at Harvard Medical School, in a press release. "But the drop in gun injuries during these large meetings attended by thousands of well-trained gun owners seems to refute the idea that gun injuries stem solely from lack of experience and training in gun use.”

In other words, when people who use guns simply aren’t using them for a week, injuries decline.

The decrease of 20 percent nationwide holds true only for men -- most who attend NRA conventions are male -- and the states in which gun ownership is highest showed the highest decreases in injuries.

This study did not alter conditions to test a theory, it just looked at statistics and drew conclusions, so it can't be said that the convention per se causes there to be fewer gun injuries. But they seem closely associated.

Some statistics: Americans own an estimated 265 million to 300 million guns. Thirty percent say they own at least one gun, and another 11 percent say they live in a household with someone who owns one, according to the Pew Research Center.

Why check on firearm injuries and the NRA convention? "No matter how one feels about guns," Jena said, in a press release, "one thing that we should all recognize is that owning and operating a firearm entails risk."

Jay-Sheree Allen, MD, is a resident in the ABC News Medical Unit.