Nearly half of working-age men who aren't in the labor force take daily pain medication, according to new research that highlights one alarming possible reason for weak labor force participation in the U.S.

Of men between the ages of 25 and 54, 47 percent said that they took pain medication during the previous day in a survey commissioned by Princeton professor and former Obama White House economist Alan Krueger. For two-thirds of those men, the medication was prescribed.

Those results line up with what Krueger found in government-conducted surveys, and they add a new explanation for low male labor force participation, namely that many men may be too sick or injured to work.

Of the men who reported taking medication, 40 percent said that pain prevented them from working.

Krueger's research, which is prepared for an upcoming Federal Reserve conference but was shared on social media Friday and has not been peer-reviewed, attributes the drop in U.S. labor force participation in recent years primarily to aging.

The analysis downplays some of the reasons that have been suggested for the drop. For instance, Krueger reports little evidence that disability insurance is increasingly a disincentive to work, as some economists have suggested.

Instead, he focuses on the possibility that some working age people, especially men, have health problems, and that getting them back to work might necessitate increasing their access to healthcare.

For younger working-age men, aged 21-30, video games also may be part of the problem, Krueger finds. While falling labor force participation for that group mostly reflects school attendance, idleness is also up. And that might be because, he finds, playing video games is more attractive than older forms of idleness, such as watching television. He discovers that young men out of the labor force spent 6.7 hours a week on average playing video games in the years 2012-2015, up from 3.6 hours a week in 2004-2007.

That finding accords with highly publicized new research by the University of Chicago's Erik Hurst and other economists that attributes some of the decline in work among young men to the improved quality of video games, which makes not working more attractive relative to working.

Again using government survey data, Krueger finds that young men and women who are out of the labor force are "remarkably content with their lives." The same is not true for older workers.