The Impact of Shift Work on Sleep, Alertness and Performance in Healthcare Workers

Abstract

Shift work is associated with impaired alertness and performance due to sleep loss and circadian misalignment. This study examined sleep between shift types (day, evening, night), and alertness and performance during day and night shifts in 52 intensive care workers. Sleep and wake duration between shifts were evaluated using wrist actigraphs and diaries. Subjective sleepiness (Karolinska Sleepiness Scale, KSS) and Psychomotor Vigilance Test (PVT) performance were examined during day shift, and on the first and subsequent night shifts (3^rd, 4^th or 5^th). Circadian phase was assessed using urinary 6-sulphatoxymelatonin rhythms. Sleep was most restricted between consecutive night shifts (5.74 ± 1.30 h), consecutive day shifts (5.83 ± 0.92 h) and between evening and day shifts (5.20 ± 0.90 h). KSS and PVT mean reaction times were higher at the end of the first and subsequent night shift compared to day shift, with KSS highest at the end of the first night. On nights, working during the circadian acrophase of the urinary melatonin rhythm led to poorer outcomes on the KSS and PVT. In rotating shift workers, early day shifts can be associated with similar sleep restriction to night shifts, particularly when scheduled immediately following an evening shift. Alertness and performance remain most impaired during night shifts given the lack of circadian adaptation to night work. Although healthcare workers perceive themselves to be less alert on the first night shift compared to subsequent night shifts, objective performance is equally impaired on subsequent nights.

Figure 1

Raster plots of the timing of work (white bars), sleep (grey bars), in-shift alertness testing (closed circles) and aMT6s acrophase (diamonds) for two intensive care doctors (a,b) and nurses (c,d). Error bars on the diamonds represent 95% confidence intervals of the timing of acrophase. Doctors worked 7 day shifts, followed by 7 day offs and 7 consecutive night shifts. Nurses worked irregular rotations between day, evening and night shifts. Night shifts were sometimes associated with frequent napping during the shifts (a) and often a small delay in circadian timing (a,c). Sleep during the day was usually considerably shorter than night sleep (b,c). Sleep duration between evening and day shift was considerably truncated (c,d). Alertness and performance data from doctors tested on the 7^th night shift are not reported in this manuscript.

Figure 2

Recruitment Flowchart.

Figure 3

Alertness, performance and subjective report for PVT performance of intensive care workers on a day shift and first and final (3^rd/4^th/5^th) night shift as measured by (a) Karolinska Sleepiness Scale, (b) subjective difficulty, (c) subjective concentration, (d) subjective motivation, (e) PVT mean reaction time (f) number of PVT lapses (g) PVT fastest 10% of reaction times and (h) maximum JDS (n = 9) during the 5-minute PVT. In all figures, higher values represent poorer outcomes. Higher values indicate increased impairment on all measures. Astericks indicate differences between shifts only at the end of shifts *p ≤ 0.05, **p ≤ 0.005, and ***p ≤ 0.001 indicates the differences in alertness and performance at the end of shifts between day and first night, day and final night and between first and final night shift.

Figure 4

Alertness and performance of intensive care workers relative to aMT6s acrophase on a day (left), first (middle) and final (3^rd–5^th) night shift (right) shown by the (a) Karolinska Sleepiness Scale, (b) PVT mean reaction time, (c) number of PVT lapses. Zero on the x-axis indicates time of acrophase, positive values represent tests before acrophase (day shift: 0–6 h, 6–12 h, 12–18 h; night shift: −12 to −5 h, −5–0 h, 0–5 h) Grey curves represent aMT6s rhythms averaged for all individuals. Striped horizontal bars represent the average main sleep prior to the start of a shift. Right panel (d) presents combined graphs of the changes in KSS, PVT mean reaction time and PVT lapses across the day, first and final night shift.