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

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 .