Standardised checklist for the assessment of methodological quality for cross-sectional (CS), case-control (CC), and prospective or retrospective cohort (PRC) studies modified from van der Windt et al,25 Hayden et al 26 and van Drongelen et al 27
| Study objective | ||
| 1. | Positive if a specific, clearly stated objective is described | CS, CC, PRC |
| Study population | ||
| 2. | Positive if the main features of the study population are described (sampling frame and distribution of the population by age and sex) | CS, CC, PRC |
| 3. | Positive if the participation rate is ≥80% or if participation rate is 60%–80% and non-response is not selective (data presented) | CS, CC, PRC |
| 3A. | Positive if the participation rate at main moment of follow-up is ≥80% or if the non-response is not selective (data presented) | PRC |
| 3A. | Positive if cases and controls were drawn from the same population and a clear definition of cases and controls was stated | CC |
| 3B. | Positive if contrast between cases and controls are big enough (controls should not be on sick leave at the time of study nor should they have been on sick leave within 6 months prior to inclusion in the study) | CC |
| Exposure assessment: shift work | ||
| 4. | Positive if data are collected and presented about shift work (starting/ending times of shifts and rotating/fixed schedule) | CS, CC, PRC |
| 5. | Method for measuring shift work: company records or personal recall during the past 3 months (+), personal recall only for a duration longer than 3 months (−) | CS, CC, PRC |
| Exposure assessment: compressed weeks | ||
| 6. | Positive if data are collected and presented about compressed weeks (no. of working hours and no. of consecutive days) | CS, CC, PRC |
| 7. | Method for measuring compressed weeks: company records or personal recall during the past 3 months (+), personal recall only for a duration longer than 3 months (−) | CS, CC, PRC |
| Outcome assessment | ||
| 8. | Method for assessing sick leave: company records or personal recall over the past 3 months (+), personal recall only for a duration longer than 3 months (−) | CS, CC, PRC |
| 8A. | Positive if data were collected for 1 year or longer | PRC |
| 8A. | Positive if exposure is measured in an identical manner in cases and controls | CC |
| Confounding assessment | ||
| 9. | Positive if data are collected and presented about occupational exposure to irregular working hours in the past | CS, CC, PRC |
| 10. | Positive if the most important confounders (age, health status) are measured and used in the analysis | CS, CC, PRC |
| 11. | Positive if data are collected and presented about the history of sick leave | CS, CC, PRC |
| 12. | Positive if confounders are measured the same for all participants using standardised methods of acceptable quality (company records or personal recall over the past 3 months) | CS, CC, PRC |
| 12A | Positive if incident cases are used (prospective enrolment) | CC |
| Analysis and data presentation | ||
| 13. | Positive if measures of association are presented (OR/RR), including 95% CIs and numbers in the analysis (totals) | CS, CC, PRC |
| 14. | Positive if the number of cases in the multivariate analysis is at least 10 times the number of independent variables in the analysis (final model) | CS, CC, PRC |
| 15. | Positive if the appropriate statistical model is used | CC |
| 15A. | Positive if a logistic regression model is used in the case of an unmatched case-control study and a conditional logistic regression model in the case of a matched case-control study | CS, PRC |