The effects of consecutive night shifts on neuropsychological performance of interns in the emergency department: a pilot study.

STUDY OBJECTIVE We obtain preliminary information on the neuropsychological performance of house officers at the beginning and end of a shift while they worked consecutive night shifts in the emergency department. METHODS We prospectively studied interns working 12-hour consecutive night shifts in an urban Level I trauma center ED. All consecutive non-emergency medicine interns rotating for 1 month were eligible except those older than 40 years and those with sleep disorders or depression (identified by using the Profile of Mood Scale, Sleep Diagnostic Questionnaire). We tested research subjects at the beginning of a day shift and at the beginning and end of night shifts 1 and 3 of 4 consecutive night shifts at times of estimated baseline wakefulness (10 PM) and maximum fatigue (3 AM). We used 3 standardized neuropsychological tests: (1) Delayed Recognition Span Test (visual memory capacity); (2) Continuous Performance Test (attentional function, vigilance); and (3) Santa Ana Form Board Test (psychomotor speed, coordination). We analyzed data with mixed-model analysis, with research subject as a random effect. RESULTS Thirteen interns were eligible, and 1 declined. Twelve interns (6 men and 6 women; age range 25 to 35 years) were enrolled. The Delayed Recognition Span Test (number correct before first error) revealed significant deterioration from the beginning of the shift to the end of the shift (mean difference -2.2; 95% confidence interval -3.1 to -1.3). This represents an 18.5% decrease in visual memory capacity. There were no significant differences found for the other tests. CONCLUSION Interns working nights demonstrated a significant reduction in visual memory capacity across the night shift. Research involving neuropsychological performance during night shifts in the ED is important. It might provide valuable insights into ways to improve our performance during night shifts.