Long hours on the job can literally make employees sick, increasing their odds of depression and heart attacks, according to a new study published by the National Bureau for Economic Research (NBER), Jeff Guo writes for the Washington Post's "Wonkblog."

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Previous research had found a correlation between working long hours and bad health but hadn't demonstrated causation. "What if naturally obsessive or anxious people gravitate to occupations where they are forced to work too much?" Guo writes. "What if the people who volunteer for overtime only do it because they need the money to solve some other crisis in their life?"

Researchers at Purdue University and the University of Copenhagen tried "to distinguish between causality and correlation" in their new NBER paper, Chong Xiang, a study co-author and professor of economics at Purdue, told "Wonkblog."

Using 1996 to 2006 data from Denmark's single-payer health system, the researchers analyzed the health of laborers and office employees. In particular, they examined Danish manufacturing companies that experienced an unexpected spike in exports due to external factors, such as foreign demand or reduced transportation costs.

Findings

The researchers found that when exports rose for external reasons, employees worked longer hours and had higher rates of injury, even after adjusting for the number of hours they worked.

They also found that women at affected manufacturing companies were more likely to take medication to prevent heart attack or stroke and more likely to be treated for severe depression.

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But despite the health challenges, employees at most companies took fewer sick days after export spikes, "indicat[ing] that they felt pressured to come in even if they weren't feeling well," Guo says. Researchers found an exception, though, at the busiest firms—those in the top 25 percent of export increases—where the number of sick days increased by 14 percent for men and 24 percent for women.

"At these places, it seems the pressure was too much and the overwork made people too sick to come in," Guo writes. He notes that researchers measured only sick days that occurred in conjunction with a drug prescription or a doctor's visit.

Men weren't as affected by the export spikes as women, which researchers attributed to women facing a higher baseline risk for stroke and depression. The men also may have been ill in other, non-observable ways, Guo notes.

"The conclusion aligns with decades of medical research hinting at similar things," Guo writes. "We've known for a while that overwork and job stress is associated with poor health ... Our jobs really are killing us" (Guo, "Wonkblog," Washington Post, 7/19).

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