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Short Report
Validity of self-reported exposure to shift work
  1. Mikko Härmä1,
  2. Aki Koskinen2,
  3. Annina Ropponen1,
  4. Sampsa Puttonen1,
  5. Kati Karhula1,
  6. Jussi Vahtera3,
  7. Mika Kivimäki1,4,5
  1. 1Modern Work and Leadership, Finnish Institute of Occupational Health, Helsinki, Finland
  2. 2ICT and Digital Services, Finnish Institute of Occupational Health, Helsinki, Finland
  3. 3Department of Public Health, University of Turku and Turku University Hospital, Turku, Finland
  4. 4Clinicum, University of Helsinki, Helsinki, Finland
  5. 5Department of Epidemiology and Public Health, University College London Medical School, London, UK
  1. Correspondence to Professor Mikko Härmä, Modern Work and Leadership, Finnish Institute of Occupational Health, Helsinki 00250, Finland; mikko.harma{at}


Objective To evaluate the validity of widely used questionnaire items on work schedule using objective registry data as reference.

Method A cohort study of hospital employees who responded to a self-administered questionnaire on work schedule in 2008, 2012 and 2014 and were linked to individual-level pay-roll-based records on work shifts. For predictive validity, leisure-time fatigue was assessed.

Results According to the survey data in 2014 (n=8896), 55% of the day workers had at least 1 year of earlier shift work experience. 8% of the night shift workers changed to day work during the follow-up. Using pay-roll data as reference, questions on ‘shift work with night shifts’ and ‘permanent night work’ showed high sensitivity (96% and 90%) and specificity (92% and 97%). Self-reported ‘regular day work’ showed moderate sensitivity (73%), but high specificity (99%) and ‘shift work without night shifts’ showed low sensitivity (62%) and moderate specificity (87%). In multivariate logistic regression analysis, the age-adjusted, sex-adjusted and baseline fatigue-adjusted association between ‘shift work without night shifts’ and leisure-time fatigue was lower for self-reported compared with objective assessment (1.30, 95% CI 0.94 to 1.82, n=1707 vs 1.89, 95% CI 1.06 to 3.39, n=1627). In contrast, shift work with night shifts, compared with permanent day work, was similarly associated with fatigue in the two assessments (2.04, 95% CI 1.62 to 2.57, n=2311 vs 1.82, 95% CI 1.28 to 2.58, n=1804).

Conclusions The validity of self-reported assessment of shift work varies between work schedules. Exposure misclassification in self-reported data may contribute to bias towards the null in shift work without night shifts.

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