Scandinavian Journal of Work, Environment & Health (Jul 2018)

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

  • Mikko Härmä,
  • Kati Karhula,
  • Annina Ropponen,
  • Sampsa Puttonen,
  • Aki Koskinen,
  • Anneli Ojajärvi,
  • Tarja Hakola,
  • Jaana Pentti,
  • Tuula Oksanen,
  • Jussi Vahtera,
  • Mika Kivimäki

DOI
https://doi.org/10.5271/sjweh.3730
Journal volume & issue
Vol. 44, no. 4
pp. 394 – 402

Abstract

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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.

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