A survey from the United States and Canada found 40 percent of police officers had symptoms of a sleep disorder, including sleep apnea and insomnia.

Officers who screened positive for those disorders were also more likely to be burned out, depressed or have an anxiety disorder. Over the next two years, they committed more administrative errors and safety violations and were more prone to falling asleep at the wheel than sound sleepers.

"In general we have this cultural attitude of, sleep is for the weak," said Dr. Michael Grandner, from the Center for Sleep and Circadian Neurobiology at the University of Pennsylvania in Philadelphia.

"When you're in an environment where signs of weakness are particularly discouraged, there may be a social pressure to not address sleep problems or to shrug them off," added Grandner, author of a commentary published with the new study in the Journal of the American Medical Association.

When police officers in particular suffer from sleep problems, he said, it becomes a public health and safety problem. "It's not just the people with sleep disorders that are affected," Grandner told Reuters Health. "If they're impaired, you're at risk."

Researchers say police departments could do more to make sure that officers with sleep disorders receive appropriate treatment, which may include sleep machines, therapy or changes in work schedules.

For the new study, close to 5,000 police officers were surveyed on sleep problems and other health topics. That included Philadelphia officers and Massachusetts state police as well as a broader range of other U.S. and Canadian cops.

The officers were on average 38 to 39 years old and most had been in the police force for more than decade. For the full study, see: http://bit.ly/hwxtTL

Dr. Charles Czeisler from Brigham and Women's Hospital in Boston and his colleagues found that 40 percent of the officers screened positive for at least one sleep disorder.

The most common was sleep apnea, which affected a third of cops, followed by moderate or severe insomnia and shift work disorder, which consists of sleepiness and insomnia associated with working at night.

Officers with a sleep disorder were more than twice as likely as healthy sleepers to report depression, emotional exhaustion or burnout and anxiety disorders on their original surveys.

On follow-up questionnaires sent out over the next two years, they were also 40 to 60 percent more likely to report making serious administrative errors, falling asleep while driving or committing a fatigue-related error or safety violation during work.

Poor sleepers reported more citizen complaints and more often showed uncontrolled anger toward a suspect or citizen.

"You have people who are sleep deprived, which means that their ability to make good decisions, to respond effectively, to drive emergency vehicles well ... all of those things are impaired," said Bryan Vila, a criminal justice professor who studies sleep and performance in cops at Washington State University in Spokane but wasn't involved in the study.

The researchers noted that being heavy increases the risk of sleep apnea, and that almost 80 percent of the officers they surveyed were overweight or obese.

Czeisler said the lowest rates of both sleep apnea and overweight and obese conditions were in Massachusetts state cops, and that that's no coincidence.

Those officers get one hour paid exercise time for every work shift, he told Reuters Health, and undergo regular fitness tests that simulate chasing a suspect or dragging a victim, with a bonus in pay if they pass.

"It's an impressive program and perhaps a model for the nation," Czeisler said.

Putting in measures to catch sleep disorders early could help prevent future health and safety consequences, researchers say. Those could include on-the-job screening in police departments, according to Czeisler, and making sure cops with sleep problems get help.

"We have great treatments for sleep disorders, we have great screening tools, the technology is there," Grandner told Reuters Health. Sleep apnea can be treated with a breathing machine and mask used at night, and behavioral therapy is often the first line of treatment for people with insomnia, he said.

For cops with shift-work disorder, cutting back on extra-long shifts and overtime hours could help.

"What are we doing with impaired cops working these critical jobs where the public safety is at risk?" Vila, also a former law enforcement officer, told Reuters Health. "This is a critical problem, and it affects a population we rely on to do some of the most sensitive things in society."

Some of the researchers reported receiving funding from pharmaceutical companies, including those that develop and manufacture sleeping pills. The current research was funded by a sleep medicine foundation as well as the U.S. Department of Justice and the Centers for Disease Control and Prevention.

Czeisler said next up is a study funded by the Federal Emergency Management Agency (FEMA) to look at sleep disorders in firefighters.