Prevalence of shift work disorder among hospital personnel: A cross‐sectional study using objective working hour data

Abstract

The prevalence of shift work disorder (SWD) has been studied using self‐reported data and the International Classification of Sleep Disorders, Second Edition (ICSD‐2) criteria. We examined the prevalence in relation to ICSD‐2 and ICSD‐3 criteria, work schedules and the number of non‐day shifts (work outside 06:00–18:00 hours) using objective working‐hours data. Secondly, we explored a minimum cut‐off for the occurrence of SWD symptoms. Hospital shift workers without (n = 1,813) and with night shifts (n = 2,917) and permanent night workers (n = 84) answered a survey (response rate 69%) on SWD and fatigue on days off. The prevalence of SWD was calculated for groups with ≥1, ≥3, ≥5 and ≥7 monthly non‐day shifts utilizing the working hours registry. ICSD‐3‐based SWD prevalence was 2.5%–3.7% (shift workers without nights), 2.6%–9.5% (shift workers with nights) and 6.0% (permanent night workers), depending on the cut‐off of non‐day shifts (≥7–1/month, respectively). The ICSD‐2‐based prevalence was higher: 7.1%–9.2%, 5.6%–33.5% and 16.7%, respectively. The prevalence was significantly higher among shift workers with than those without nights (p‐values <.001) when using the cut‐offs of ≥1–3 non‐day shifts. Shift workers with nights who had ≥3 days with ICSD‐3‐based SWD symptoms/month more commonly had fatigue on days off (49.3%) than those below the cut‐off (35.8%, p < .05). The ICSD‐3 criteria provided lower estimates for SWD prevalence than ISCD‐2 criteria, similarly to exclusion of employees with the fewest non‐day shifts. The results suggest that a plausible cut‐off for days with ICSD‐3‐based SWD symptoms is ≥3/month, resulting in 3%–6% prevalence of SWD.

How to schedule night shift work in order to reduce health and safety risks

“…If the night shift worker suffers from shift work disorder, defined as having shift work-related sleep problems and/ or excessive sleepiness, one would assume that the sleep disturbances are chronic. The prevalence of shift work disorder is higher among night shift workers than shift workers who alternate between day and evening work, and shift work disorder is also positively correlated with frequency of night shifts in the shift schedule (25,26).…”

“…Taken together, night shift work has several shortterm physiological effects: circadian disruption is introduced, levels of melatonin are modestly suppressed, circadian rhythms are desynchronized, sleep duration is reduced, and sleepiness is increased. The short-term physiological effects appear to depend on how the night shifts are scheduled (20,25,26,(31)(32)(33)(34)(35)(36)(37)(38). The shortterm physiological effects are suggested to link night shift work to acute safety risks and possibly long-term health effects, although studies specifically addressing whether these acute effects serve as mediators of longterm health and safety risks are lacking.…”

Cognitive behavioural therapy interventions for insomnia among shift workers: RCT in an occupational health setting

“…The shift work inclusion criteria for our study was also quite loose (only a 10% minimum of shifts had to be other than day shifts), making the generalizability of the results more uncertain because shift workers' working times and the circadian disruption and misalignment related to these vary greatly. Although most of our participants clearly exceeded the minimum criteria, future studies should consider stricter, multi-dimensional criteria (Harma et al 2015;Vanttola et al 2019). We should also note that the overall sample was quite small and three out of four participants were women.…”

Employees with shift work disorder experience excessive sleepiness also on non-work days: a cross-sectional survey linked to working hours register in Finnish hospitals

“…To focus on fluctuating circadian disturbance, we excluded permanent day workers (n=3,207), shift workers without night shifts (n=2,227), and permanent night workers (n=106), since they had less than three types of shifts. We excluded employees who did not answer the questions that were used to define SWD cases (n=171), and employees who had less than three non-day shifts (work outside 06:00–18:00 h) per month (n=26) 10 ) . The final sample included 2,900 shift workers who had at least three non-day shifts per month including at least one night shift (at least three h of work during 23:00–06:00) per month in accordance with our recent result on a minimum cut-off for the occurrence of SWD symptoms 10 ) .…”

“…We have recently found that up to 18% of hospital employees whose work include night shifts find shift working hours difficult and develop shift work disorder (SWD) 10 ) . SWD is characterized by shift work-related insomnia and/or excessive sleepiness based on the second edition of the International Classification of Sleep Disorders (ICSD-2) criteria 11 ) , and it is referred to as circadian rhythm sleep-wake disorder (shift work type) in the 11th revision of the International Classification of Diseases (ICD-11) 12 ) .…”