Table 3 Checklist for the assessment of methodological quality of the reviewed studies

 1. Sampling method

  A. Nonprobability sampling (including purposive, quota, convenience and snowball sampling)

0

  B. Probability sampling (including simple random, systematic, stratified g, cluster, two-stage and multi-stage sampling) or registry (i.e., full sample/all workers)

1

 2. Was the response rate reported?

  A. Not reported

0

  B. Response rate below 50%

0

  C. Response rate at 50% or above

1

 3. Are the individuals selected to participate in the study likely to be representative of the target population?

  A. No

0

  B. Yes

1

 4. Selection bias: Is there a risk of selection bias caused by the inadequate selection of participants?

 A. High risk

0

 B. Low risk

1

 5. Is the sample size adequate for establishing relationships (assumption of statistical power)?

  A. No

0

  B. Yes

1

 6. How was working time assessed?

  A. Self-report

0

  B. Objective data (including registries and payroll records)

1

 7. How was sickness absence assessed?

  A. Self-report

0

  B. Objective data (including registries and payroll records)

1

 8. Performance bias: Is there a risk of bias caused by the inadequate measurement of exposure?

  A. High risk

0

  B. Low risk

1

 9. Are the statistical methods appropriate for the study design?

  A. No/Can’t tell

0

  B. Yes

1

 10. Were meaningful demographic covariates included?

  A. No

0

  B. Yes

1

 11. Were other work factors adjusted for?

  A. No

0

  B. Yes

1

 12. Is the study design cross-sectional or prospective (with time-lag)?

  A. Cross-sectional

0

  B. Prospective

1

 13. Was previous sickness absence adjusted for in prospective analyses?

  A. No

0

  B. Yes

1

 14. Confounder bias: Is there a risk of bias caused by the inadequate confirmation and consideration of confounding variable?

  A. High risk

0

  B. Low risk

1