Syracuse, N.Y. ? American workers should stop trying to be heroes and just stay home when they’re sick– it could be cheaper for their employers, according to a study.

Workers who come in sick cost their employers an average of $255 each per year, according to Cornell University labor researchers.

Sick employees have difficulty concentrating, work more slowly and have to repeat tasks, bogging down productivity, according to the study. They also get their co-workers sick, but those costs were not counted in the study.

Economists refer to slack productivity from ailing workers as “presenteeism,” and the Cornell study said it might cost employers even more than absenteeism due to illness.

Other studies have suggested that presenteeism costs U.S. businesses $180 billion annually in lost productivity.

“The study doesn’t mean people should stay home sick at every sniffle,” said Ron Goetzel, director of Cornell’s Institute for Health and Productivity Studies in Washington, which conducted the research.

“It says this is a very large category of expenses, even exceeding the costs of absenteeism and medical and disability benefits, and part of the problem is that employers have not yet fully recognized the financial impact it can have on their business.”

The impact of employee absenteeism is well documented. Figuring out how much it costs to come to work sick, however, has been more elusive, because of a lack of accepted measurement standards.

Lori Rosen, a workplace analyst for CCH Inc., a Riverwoods, Ill.-based trade group that does an annual nationwide survey on absenteeism, acknowledged presenteeism is a problem but said absenteeism still costs employers more, an average of $645 per employee per year.

“Presenteeism might be more costly if you have an employee start an epidemic and you knock out the whole office,” Rosen said. “With absenteeism, though, you have to consider overtime, hiring a temp, and a whole bunch of other costs besides the work not getting done.”