Sleep and cognitive performance of flight nurses after 12-hour evening versus 18-hour shifts.

Background: Inadequate rest can result in disastrous medical and aviation errors. Using a prospective within-subjects design, this study compared the amount of daily sleep and the cognitive performance in flight nurses working 12-hour evening versus 18-hour shifts during a 72-hour duty schedule.

Methods: Ten flight nurses who worked two different duty schedules participated in the study. The first duty schedule consisted of three back-to-back 12-hour (7:00 pm to 7:00 am) evening shifts. The second duty schedule consisted of two 18-hour (7:00 am to 1:00 am) shifts separated by a 24-hour rest period. Pre- and duty sleep times were monitored using actigraphy. The flight nurses were tested using a battery of neuropsychological tests before and immediately after completing 12- and 18-hour duty schedules. After the conclusion of both duty schedules, nurses were asked to rate the 12- versus 18-hour duty schedules via questionnaire.

Results: Daily sleep times for the 12- versus 18-hour were not different for the pre-duty schedule (8.9 +/- 2.3 vs. 9.0 +/- 2.3 hours) or during duty schedule (7.0 +/- 1.4 vs. 6.9 +/- 1.3 hours). A significant decline was seen in the amount of pre- versus duty sleep for both the 12-hour (8.9 +/- 2.3 vs. 7.0 +/- 1.4 hours; P < .05) and the 18-hour (9.0 +/- 2.3 vs. 6.9 +/- 1.3 hours; P = .04) duty schedules. During the 72-hour duty schedule, the 12-hour vs. 18-hour duty schedules, the nurses had less pre-shift sleep (3.2 +/- 1.2 vs. 6.2 +/- 0.6; P = .001) and more on-shift (4.4 +/- 1.7 vs. 2.1 +/- 0.8; P = .002) sleep. Despite the decline in daily sleep during both duty schedules, no significant decline in the before versus after cognitive test scores were observed for either the 12- or 18-hour duty schedule. A questionnaire given to the 10 nurses indicated that the 18-hour duty schedule was more compatible with their non-work lifestyle (P = .04).

Conclusions: Provided adequate daily sleep (at least 7 hours/day) is obtained, we found no difference or decline in the cognitive function of flight nurses working either a 12-hour evening or 18-hour shift during a 72-hour duty schedule. Eighteen-hour duty shifts may be a practical economical means of expanding the period of helicopter site coverage without adversely affecting cognitive performance in medical crewmembers. Actigraphy may be a useful tool for air medical programs that want to objectively assess whether adequate sleep is occurring in individuals working extended (>12 hours) or unusual duty shifts.