Work schedules and levels of sleepiness among medical residents long have been a source of concern. A pilot study in the May-June issue of the Journal of Hospital Medicine shows nurses—especially those in high-stress specialties like intensive care—also could benefit from an extra 40 winks.
Lead author Salim Surani, MD, of the Baylor College of Medicine, and colleagues compared sleepiness in 10 intensive care unit (ICU) nurses to those of 10 floor nurses, all of whom worked night shifts beginning at 7 p.m. and ending at 7 a.m.
Sleepiness was assessed in three ways. On the morning after the third or fourth shift, each nurse underwent a modified version of the Multiple Sleep Latency Test (MSLT), which measured the time it took for them to fall asleep during two nap periods, one at 7:15 a.m., another at 8:30 a.m. Sleep latency less than five minutes is considered severely pathological. Before the MSLT, they filled out the Epworth Sleepiness Scale (ESS), a questionnaire designed to explore the subject’s chances of falling asleep under six different scenarios. The ESS is considered a well-standardized and validated measure of subjective sleepiness, with a score more than eight considered abnormal.
Finally, for the week leading up to the day of the test, the nurses maintained a sleep diary, recording their bedtimes, wake times, daytime naps, nocturnal awakenings, and comments about their feelings of sleepiness. Each participant received a $25 gift certificate at the completion of the study.
ICU nurses were chosen because they typically “must make extremely critical judgments; they must be alert enough to recognize abnormalities in their patients and react quickly enough when something goes wrong,” coauthor Shyamsunder Subramanian, MD, says. These demands take their toll, as some studies show ICU nurse burnout rates as high as 33%, leading the investigators to hypothesize that ICU nurses also would report feeling sleepier and having poorer sleep quality than floor nurses.
The results bore out the hypothesis. Among ICU nurses, the mean ESS score was 8.7, compared with a mean of 5.6 for the floor nurses (p=0.042). All in all, seven of the 10 ICU nurses had a score more than eight, compared with only two of the 10 floor nurses (p<0.005).
Similarly, the mean MSLT for the first nap period was 4.7 minutes for the ICU nurses and 10.9 minutes for the floor nurses (p=0.025), with nine of the 10 ICU nurses falling asleep in less than five minutes, compared with two of the floor nurses (p<0.005). ICU nurses also had a shorter MSLT overall, of 6.1 minutes, versus 10.6 minutes for the floor nurses, but this difference was not statistically significant. There also was no significant difference between the groups in mean nightly sleep time: ICU nurses reported a total 405 minutes, while the floor nurses clocked in at 416 minutes.
There are two probable interpretations of the data, said Dr. Subramanian, director of sleep services at Baylor. Perhaps it is simply too exhausting for people to function at a peak level of alertness, particularly in a demanding specialty like intensive care, for 12 hours. Or it could be burnout was as common among the ICU nurses in this study as it was for their colleagues in other studies, as reflected in their ESS scores, which rival the scores observed in people with depression or chronic illness and suggest a lower quality of everyday sleep. The findings most likely result from a combination of these factors, he notes.