Table 1

Methodological quality appraisal of the included studies

Study IDAyas et al40Barger et al41Firth-Cozens42Fisman et al43Hayasaka et al44Kirkcaldy et al45Rosta and Aasland46Stamp et al47Sundquist and Johansson48Varma et al49Zahrai et al50
1ObjectivesAre the objectives or hypotheses of the research described in the paper?11111111111
2Study designIs the study design presented?11111111111
3aTarget populationDo the authors describe the target population they wanted to research?11111111111
3bSampleWas a random sample of the target population taken? AND was the response rate 60% or more?0.50.510.
3cSampleIs participant selection described?11110.5101111
3dSampleIs participant recruitment described, or referred to?11111111110
3eSampleAre the inclusion and/or exclusion criteria stated?11110.50.511110.5
3fSampleIs the study sample described? (minimum description: sample size, gender, age and occupation)11011100011
3gSampleIs the number of participants at each stage of the study reported?1110.510.511111
4VariablesAre the measures of long working hours and the health outcome described?110.511111111
5aData sources, collectionDo authors describe the source of their data (eg, official registry, health survey) AND how were the data collected?11111111111
5bMeasurementWas reliability of the measure(s) of long working hours mentioned or referred to?00010001010
5cMeasurementWas the validity of the measure(s) of long working hours mentioned or referred to?11000000000
5dMeasurementWere health outcomes assessed by objective measures or validated self-reporting instruments?01111011111
6aStatistical methodsWere appropriate statistical methods used and described, including those for addressing confounders?0.510.510.50.510.5110.5
6bStatistical methodsWere the numbers/percentage of participants with missing data for long working hours and the health outcome indicated AND If more than 20% of data in the primary analyses were missing, were methods used to address missing data?0000.50000010.5
Total score* (%)12.0 (75)13.5 (84)11.0 (69)13.5 (84)11.0 (69)10.0 (63)10.5 (66)12.5 (78)12.0 (75)15.0 (94)11.0 (69)
Quality rate†intermhighintermhighintermintermintermintermintermhighinterm
  • low=<60; intermediate (interm)=60–79; high=80–100.

  • *Maximum score=16.

  • †Quality rate (%).