Study author Linda D. Scott of Grand Valley State University in Grand Rapids, Mich., analyzed data collected from 895 full-time hospital staff nurses, who completed logbooks on a daily basis for four weeks providing information concerning work hours, sleep duration, drowsy and sleep episodes at work, and drowsy driving occurrences.

The study, published in the journal Sleep, found nearly 67 percent of the nurses reported at least one episode of drowsy driving, and 3 percent reported experiencing drowsy driving following every shift worked. On average, nurses reported experiencing an episode of drowsy driving one out of every four shifts they worked.

Scott said 281 episodes of motor vehicle crashes/near-motor vehicle crashes were reported during the study period -- the majority followed nursing shifts that exceeded 12.5 hours.

The study also found that almost two-thirds of the nurses reported struggling to stay awake at work at least once during the study period and 17 percent fell asleep at least once during their shifts.