Health > Long work hours may raise injury risk

NEW YORK (Reuters Health) - Working beyond the standard 8-hour day may raise the risk of job-related injuries, regardless of a person's occupation, a new study suggests.

Among nearly 10,800 U.S. adults followed for 13 years, researchers found that those who worked overtime or on regularly extended shifts were at greater risk of on-the-job injuries. And the effect was not limited to hazard-fraught industries.

Muscle and joint problems were the most common complaint, followed by cuts and bruises, according to findings published in the journal Occupational and Environmental Medicine.

Some past research has shown that people who work long hours tend to sustain more injuries and health problems than workers with standard 40-hour weeks. But these studies have often been limited by shortcomings in their methodology, according to Dr. Allard Dembe, the lead author of the new study.

A central question has been whether the findings reflect the fact that overtime and long work days are often found in inherently dangerous industries, like manufacturing, construction and trucking.

But in their study, Dembe and his colleagues found that longer work hours appeared to raise injury risk even when job type and other factors -- such as a worker's age and gender -- were weighed.

This strengthens the argument that something about long work hours themselves makes people more vulnerable to injury, said Dembe, an associate professor at the University of Massachusetts Medical School in Shrewsbury.

That something, he told Reuters Health, could be stress and fatigue, which can make workers more prone to mistakes and mishaps.

The study findings are based on data from a U.S. survey that has followed the same group of people since 1979. The researchers analyzed data collected from 10,793 participants between 1987 and 2000, starting when the men and women were between the ages of 22 and 30.

Workers were considered to have logged long hours if their jobs sometimes included overtime -- meaning beyond the usual 40-hour week -- or if they regularly worked 12-hour days or 60-hour weeks.

Overall, there were more than 5,100 work-related injuries or health problems during the study period, with more than half occurring in jobs with long hours.

People who normally worked long shifts were 37 percent more likely to sustain an injury than their peers who worked shorter hours. Those who worked overtime were at 61 percent greater risk than workers whose jobs included no overtime.

The fact that overtime seemed to be a greater injury risk than regularly extended shifts is one of the most interesting findings from the study, Dembe said.

He suspects that periodically working overtime may set people up for more injuries because they're not used to the schedule.

"It's something that's not routine. It's over and above what you usually do," Dembe noted.

He also pointed out that in the U.S., up to one third of the overtime hours people log are mandatory. Mandatory overtime may create tension and stress for some workers, which could contribute to injury risk, Dembe said.

But whether that's the case is unclear, as the study data didn't separate mandatory from voluntary overtime.

If long work hours are in fact a risk factor for injury, a potential preventive measure could be to ensure employees get adequate "rest breaks," according to Dembe. These, he said, could take the form of both short breaks during the day, as well as days off -- with, for example, limits on how many days in a row an employee can work extended hours.

SOURCE: Occupational and Environmental Medicine, September 2005.

2005-09-03