Would you believe that a lot of police officers could be sleeping on-the-job? That’s the upshot of a new study that found that nearly half of officers suffer from a potentially deadly sleep condition, like sleep apnea. Experts warn that sleep-deprived officers are a threat to themselves and you, since they’re more likely to do everything from cause car accidents to fall asleep while on patrol.

Researchers at Brigham and Women’s Hospital in Massachusetts had 5,000 police officers complete questionnaires that asked things like, “How long does it take you to fall asleep at night?” and “Have you fallen asleep while driving in the last month?” Then, they gave the officers a basic physical to gauge their overall health.

The result? Nearly half had at least one sleep disorder. The most common one? Obstructive sleep apnea, which causes you to stop breathing for up to 30 seconds while you sleep, so you keep partially waking up all night struggling to breathe.

Also, the study found that officers with sleep disorders were drastically more likely to engage in risky on-the-job behavior. Everything from falling asleep while driving, to experiencing uncontrollable rage while speaking with the public, compared to officers without sleep disorders. But experts say that the most shocking finding was that most of the officers didn’t have a clue that they were suffering from a sleep disorder, so they weren’t being treated.

So, why do so many officers suffer from sleep disorders? Researchers say that police officers work varied shifts and if they’re working on a big case, it’s common for them to log in 24-hour days. So, their body’s sleep routine is constantly disrupted. Experts say that more studies need to be done. But police stations everywhere are already creating new procedures to help officers get more rest.