Association of changes in work shifts and shift intensity with change in fatigue and disturbed sleep: a within-subject study

• Published in: Scandinavian Journal of Work, Environment ＆ Health Vol. 44; no. 4; pp. 394 - 402
• Main Authors: Härmä, Mikko, Karhula, Kati, Ropponen, Annina, Puttonen, Sampsa, Koskinen, Aki, Ojajärvi, Anneli, Hakola, Tarja, Pentti, Jaana, Oksanen, Tuula, Vahtera, Jussi, Kivimäki, Mika
• Format: Journal Article
• Language: English
• Published: Finland Scandinavian Journal of Work, Environment ＆ Health 01.07.2018; Nordic Association of Occupational Safety and Health (NOROSH); Scandinavian Journal of Work, Environment & Health
• Subjects: Adult; Age Factors; Confidence intervals; disturbed sleep; Employees; Fatigue; Fatigue - psychology; Female; forward-rotating shift; Humans; insomnia; Longitudinal Studies; Male; Middle Aged; night shift; Night shifts; night work; Nighttime; Occupational stress; older worker; Original article; Personnel, Hospital - statistics & numerical data; Public sector; Regression analysis; shift; shift intensity; shift interval; Shift work; Shift Work Schedule; shift worker; Sleep; Sleep deprivation; Sleep disorders; sleep duration; sleep length; sleep problem; Sleep Wake Disorders - epidemiology; sleepiness; Statistical analysis; Studies; Surveys and Questionnaires; within-subject study; Work Schedule Tolerance; Workers; Working hours; night shift; sleep duration; shift work; sleep problem; sleep length; working hours; shift worker; insomia; older worker; sleepiness; forward-rotating shift; shift interval
• DOI: 10.5271/sjweh.3730
• ISSN: 0355-3140; 1795-990X

Objectives: The aim of this study was to examine whether changes in work shifts and shift intensity are related to changes in difficulties to fall asleep, fatigue, and sleep length. Methods: Questionnaire responses of hospital employees (N=7727, 93% women) in 2008, 2012, 2014 and 2015 were linked to daily-based records of working hours during three months preceding each survey. We used conditional logistic regression and longitudinal fixed-effects analyses to investigate odds ratios (OR) and 95% confidence intervals (CI) for each 25% within-individual change in the proportion of working hour characteristics in relation to changes in fatigue, difficulties to fall asleep, and 24-hour sleep length. Results: Change in night but not in morning or evening shifts was associated with parallel changes in odds for longer sleep length (OR 1.45, 95% CI 1.28-1.64) and fatigue during free days (OR 1.38, 95% CI 1.16-1.64). Similarly, short shift intervals and having ＞2 but not ＞4 consecutive night shifts were associated with increased odds of fatigue during work and difficulties to fall asleep (OR 1.42, 95% CI 1.19-1.72 and OR 1.10, 95% CI 1.05-1.19, respectively). Among workers aged ≥50 years, the associations were the strongest between night shifts and longer sleep (OR 2.24, 95% CI 1.52-3.81) and between higher proportion of short shift intervals and fatigue during free days (OR 1.68, 95% CI 1.10-2.54). Conclusions: Among shift workers with fatigue or sleep problems, decreasing the proportion of night shifts and quick returns and giving preference to quickly forward-rotating shift systems may reduce fatigue.