April 17 (HealthDay News) -- Common job-related problems such as conflicts with bosses or co-workers are more likely than long hours, night shifts or job insecurity to cause poor sleep.

That's the conclusion of a study by University of Michigan researchers who analyzed data from two surveys of about 2,300 U.S. adults who were followed for up to a decade. During that time, about half of the participants said they had trouble sleeping.

"Together, work and sleep take up about two-thirds of every weekday. But until now, very little research has focused on the connections between work and sleep for the average U.S. worker," Sarah Burgard, an assistant professor of sociology and an assistant professor of epidemiology, said in a prepared statement.

In their analysis of the survey data, Burgard and graduate student Jennifer Ailshire found that work conditions affected sleep patterns, instead of the other way around. Respondents who frequently felt upset or bothered at work, or had ongoing conflicts with bosses or co-workers, were about 1.7 times more likely than others to experience sleep problems.

"Massive changes over the past half-century have reshaped the workplace, with major implications for sleep. For many workers, psychological stress has replaced physical hazards," Burgard said. "Physical strain at work tends to create physical fatigue and leads to restorative sleep, but psychological strain has the opposite effect, making it more difficult for people to sleep."

There was no evidence that long hours or working nights or weekends led to poor sleep quality.

The researchers did find that work-family conflicts and having children under the age of 3 were significant predictors of sleep problems. People with children under the age of 3 were about 2.2 times more likely to report poor sleep quality.

The study was presented April 17 at the annual meeting of the Population Association of America, in New Orleans.

Burgard said she plans to examine how to protect workers from negative working conditions and how to prevent work problems from affecting sleep.

SOURCE: University of Michigan, news release, April 17, 2008