Deterioration of neurobehavioral performance in resident physicians during repeated exposure to extended duration work shifts

Abstract

Study objectives: Although acute sleep loss during 24- to 30-h extended duration work shifts (EDWS) has been shown to impair the performance of resident physicians, little is known about the effects of cumulative sleep deficiency on performance during residency training. Chronic sleep restriction induces a gradual degradation of neurobehavioral performance and exacerbates the effects of acute sleep loss in the laboratory, yet the extent to which this occurs under real-world conditions is unknown. In this study, the authors quantify the time course of neurobehavioral deterioration due to repeated exposure to EDWS during a 3-week residency rotation.

Design: A prospective, repeated-measures, within-subject design.

Setting: Medical and cardiac intensive care units, Brigham and Women's Hospital, Boston, MA.

Participants: Thirty-four postgraduate year one resident physicians (23 males; age 28.0 ± 1.83 (standard deviation) years)

Measurements and results: Residents working a 3-week Q3 schedule (24- to 30-h work shift starts every 3(rd) day), consisting of alternating 24- to 30-h (EDWS) and approximately 8-h shifts, underwent psychomotor vigilance testing before, during, and after each work shift. Mean response time, number of lapses, and slowest 10% of responses were calculated for each test. Residents also maintained daily sleep/wake/work logs. EDWS resulted in cumulative sleep deficiency over the 21-day rotation (6.3 h sleep obtained per day; average 2.3 h sleep obtained per extended shift). Response times deteriorated over a single 24- to 30-h shift (P < 0.0005), and also cumulatively with each successive EDWS: Performance on the fifth and sixth shift was significantly worse than on the first shift (P < 0.01). Controlling for time of day, there was a significant acute (time on shift) and chronic (successive EDWS) interaction on psychomotor vigilance testing response times (P < 0.05).

Conclusions: Chronic sleep deficiency caused progressive degradation in residents' neurobehavioral performance and exacerbated the effects of acute sleep loss inherent in the 24- to 30-h EDWS that are commonly used in resident schedules.

Keywords: Extended duration work shift; acute; chronic; graduate medical education; psychomotor vigilance test; resident; sleep deficiency.

Figure 1

A flow chart showing subject progression through the study stages (for years 1 and 2 of the study).

Figure 2

Cumulative total sleep time during the residents' intensive care unit (ICU) schedule including nocturnal sleep and diurnal naps in comparison with cumulative sleep over 14 days prior to the ICU rotation (including 7 days of projected cumulative sleep; dotted lines, open circle). Compared with daily sleep duration (7.75 h; 95% confidence interval 6.5-9.0 h) obtained when not on alternating extended duration shifts, when on a schedule including alternating 30-h shifts residents obtained 10.9 h less sleep by day 7, 20.4 h less sleep by day 14, and a projected 30.6 h less sleep by day 21, n = 34.

Figure 3

Mean change in mean PVT reaction time (RT) (A), lapses (B), and slowest 10% RTs (C) over the duration of an extended shift. Post hoc differences are shown (***P < 0.0005; **P < 0.001; *P < 0.005).Mean ± standard error of the mean reported, n=33.

Figure 4

Degradation of neurobehavioral performance over 6 successive extended duration shifts on a 21-day rotation. Change in mean PVT reaction time (RT) (A), number of lapses (B), and slowest 10% RTs (C) from EDWS1 to EDWS6. Post hoc differences are shown (***P < 0.0005; **P < 0.001; *P < 0.005).Mean ± standard error of the mean reported, n = 31.

Figure 5

Interaction of chronic and acute effects: change in performance from the start of the extended duration work shift (Day 1 – 06:00-14:59) to the end of the extended duration work shift (06:00-14:59) mediated by the effects of each successive extended duration shift. Performance at the end of the shift shows greater chronic effects, whereas performance at the start of shifts remains relatively protected. Mean ± standard error of the mean reported,n = 34.

Figure 6

Psychomotor vigilance test (PVT) cumulative reaction time (RT) distribution (left panel) with means and 95% confidence intervals and Weibull function parameters fitted to cumulative RT distribution (right panel). These data represent the average RT percentiles (mean ± 95% confidence intervals) and the fitted cumulative distribution function (4-parameter Weibull) from PVTs completed at the start and end of the first and sixth extended duration work shift (EDWS). The top and bottom axis represents log-transformed RTs and equivalent mean RTs, respectively. The y-axis represents the percentile value. A rightward shift corresponds to an overall cognitive slowing, and a stretching of the tail indicates increased variability and long RTs. Data distribution at the end of the first EDWS (EDWS 1 – End (open circle) was strikingly similar to the start of the sixth extended duration work shift (EDWS 6 – Start (filled triangle). Data distribution at the end of the EDWS suggests increased cognitive slowing and increased variability due to long RTs. The end of the sixth EDWS was associated with significantly greater variability than the start and end of the first shift, and enhanced cognitive slowing (offset midpoint), (n = 34). ^†P < 0.03, ^‡P < 0.0005. ^aMeasure of skew (1.0 = exponential). ^bSpread of distribution reflecting variability. ^cLeading edge of RT (fastest possible response). ^dMidpoint (50^th percentile) - cognitive slowing.