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Shift work directly causes circadian disruption and reduces sleep quality. Physical activity is also associated with sleep quality. However, no study has reported the relationship between a specific level of physical activity and sleep quality. This study aimed to investigate the relationship between sleep quality and the amount of physical activity by stratifying subjects into gender and shift‐work subgroups. Among those who participated in the Kangbuk Samsung Health Study in 2016–2017, data from 185,958 full‐time workers were analysed. We evaluated their physical activity by metabolic equivalents (METs‐min/week), sleep quality and shift work. A chi‐squared test, a t test and logistic regression analysis were performed. An increase in sleep quality was found for the group with physical activity of 600–9,000 METs‐min/week compared to that in the sedentary group among all subjects. In female day workers, the sleep quality of the group with 600–6,000 METs‐min/week was significantly higher (odds ratio [OR], 0.760; 95% confidence interval [CI], 0.673–857) than that in the sedentary group. In male day workers, sleep quality increased when physical activity was increased up to 6,000–9,000 METs‐min/week (OR, 0.760; 95% CI, 0.673–857). In female shift workers, there was no significant difference in sleep quality according to physical activity level. In male shift workers, sleep quality was better in the group with physical activity of 1,800–3,000 METs‐min/week (OR, 0.826; 95% CI, 0.692–0.986) or 3,000–6,000 METs‐min/week (OR, 0.771; 95% CI, 0.642–0.926). Optimal physical activity is good for sleep quality. The sleep quality of females is significantly worse than that of males in both day and shift workers. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the association between shift work disorder and mental health in hospital‐based nurses. Staff completed an online survey comprising demographic questions, the Shift Work Disorder Questionnaire, Patient Health‐9 and the General Anxiety Disorder‐7 scale. Sick leave data were collected from archival records from the Human Resources Department. Two hundred and two nurses (95% female; age M = 35.28 years ± SD = 12) participated (42% of eligible staff). Those at high risk of shift work disorder had higher depression (M = 7.54 ± SD = 4.28 vs. M = 3.78 ± SD = 3.24; p < 0.001) and anxiety (M = 5.66 ± SD = 3.82 vs. M = 2.83 ± SD = 3.33, p < 0.001) compared to those at low risk. Linear regression models showed that being at high risk of shift work disorder was the most significant predictor of depression, explaining 18.8% of the variance in depression (R2 = 0.188, adjusted R2 = 0.184, F(1, 200) = 46.20, p < 0.001). Shift work disorder combined with the number of night shifts and alcoholic drinks on non‐work days accounted for 49.7% of the variance in anxiety scores (R2 = 0.497, adjusted R2 = 0.453, F(3, 35) = 11.51, p < 0.001). Mean sick leave in those with high risk of shift work disorder was 136.17 hr (SD = 113.11) versus 103.98 hr (SD = 94.46) in others (p = 0.057). Depression and years of shift work accounted for 18.9% of the variance in sick leave taken (R2 = 0.189, adjusted R2 = 0.180, F(2, 175) = 20.36, p < 0.001). Shift work disorder is strongly associated with depression and anxiety, providing a potential target to improve mental health in shift workers. Depression, in turn, is a significant contributing factor to sick leave. [ABSTRACT FROM AUTHOR]