Validity of self-reported exposure to shift work.
To evaluate the validity of widely used questionnaire items on work schedule using objective registry data as reference.



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.



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).



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.
Modern Work and Leadership, Finnish Institute of Occupational Health, Helsinki, Finland.
Mikko
M
Härmä
ICT and Digital Services, Finnish Institute of Occupational Health, Helsinki, Finland.
Aki
A
Koskinen
Modern Work and Leadership, Finnish Institute of Occupational Health, Helsinki, Finland.
Annina
A
Ropponen
Modern Work and Leadership, Finnish Institute of Occupational Health, Helsinki, Finland.
Sampsa
S
Puttonen
Modern Work and Leadership, Finnish Institute of Occupational Health, Helsinki, Finland.
Kati
K
Karhula
Department of Public Health, University of Turku and Turku University Hospital, Turku, Finland.
Jussi
J
Vahtera
Modern Work and Leadership, Finnish Institute of Occupational Health, Helsinki, Finland.|Clinicum, University of Helsinki, Helsinki, Finland.|Department of Epidemiology and Public Health, University College London Medical School, London, UK.
Mika
M
Kivimäki
D015982:Bias; D015331:Cohort Studies; D005221:Fatigue; D005260:Female; D005387:Finland; D006761:Hospitals; D006801:Humans; D016015:Logistic Models; D008297:Male; D012042:Registries; D057566:Self Report / Q000592:standards*; D011795:Surveys and Questionnaires / Q000592:standards*; D014940:Work Schedule Tolerance
Methodology; speciality