Table 2

Characteristics of the included studies

Study IDCountry of study populationDesign*SettingParticipants and sample size (response rate)Working hoursHealth outcomesQuality score (%)
Ayas et al40USACohort, prospective (1 year)/case cross-overHospitalInterns in postgraduate residency programs
Sample size: 2737 (80%)
Mean (SD) hours worked/month: 249.8 (75.3). Self-reported, monthly survey. Strong correlation (Pearson r=0.76; p 0.001) with hours worked 244 (69.3) from work diaries of randomly selected subset of 192 interns. Extended periods (20 or more consecutive hours) vs non-extended periods (12 h or less consecutive hours)Self-reported percutaneous injuries12.0 (75)
Barger et al41USACohort, prospective (1 year)HospitalResidents first postgraduate year (interns)
Sample size: 2737 (80%)
Mean (SD) hours worked/week 70.7 (26.0). Extended shift (≥24 h) vs non-extended shift (<24 h). Self-reported, validatedSelf-reported and documented motor vehicle crashes13.5 (84)
Firth-Cozens42UKCohort, prospective (1 year)HospitalJunior house officers
Sample size: 170 (72%)
Mean number of hours/week=90.6 h (include on call). Self-reportedGHQ-12 (case: score ≥2) and SCLDS, self-reported11.0 (69)
Fisman et al43USA and CanadaCase-crossoverHospitalMedical trainees vs other HCW.
Sample size: 109 vs 241 (46%)
Median number of hours per week: medical trainees=70; other HCW=40 (p<0.001). Self-reported, high reliabilityReported percutaneous injuries to employee healthcare service13.5 (84)
Hayasaka et al44JapanCross-sectionalHospital, clinics, otherFemale physicians
Sample size: 367 (63%)
Comparison of increasing number of hours/week from ≤30 to >50, self-reportedGHQ-30 (case: score ≥8), self-reported11.0 (69)
Kirkcaldy et al45GermanyCross-sectionalNot specifiedMedical and dental practitioners. Sample size: 2500 (not specified)Long hours: mean 58.36 h/week SD 9.16
Short hours: mean 38.17 h/week SD 7.72
Self-reported
Self-reported traffic accidents10.0 (63)
Rosta and Aasland46Germany and NorwayCross-sectionalHospitalHospital physicians
Participants: 1917 (58%) in Germany and 1072 (65%) in Norway answered the questionnaire.
From survey responders, 1260 (65.7%) Germans and 562 (52.4) Norwegians were included in the analysis after applying further inclusion criteria
German vs Norwegian physicians (%):
Hours per day >9=58.8 vs 26.7
60 h on-call per month=63.4 vs 18.3
Self-reported
Validated questionnaire on self-rated health10.5 (66)
Stamp et al47USABefore-and-afterHospitalResidents of general surgery
Sample size: 28 (97%)
Changes of work patterns, after reduction from 90–110 to 78–80 work hours/weekSF-36, mental health; BDI, depression; self-reported12.5 (78)
Sundquist and Johansson 48SwedenCross-sectionalPrimary careGeneral practitioners
Sample size: 1004 (72%)
Overtime defined as working at least 47 h/week. Self-reportedSwedish SF-36, impaired mental health, self-reported12.0 (75)
Varma et al49DenmarkCohort, prospective (20 months)HospitalSenior medical consultants
Sample size: 2790 (62%)
Long work hours (>40 h/week). Self-reportedDepression: redemption of anti-depressive drug prescriptions15.0 (94)
Zahrai et al50CanadaCohort, prospective (6 months)HospitalOrthopaedic surgery residents
Sample size: 16 (not specified)
Night float (n=9): 77.8% did >80 h/week at baseline; 71.4% at follow-up
Standard call (n=7): 57.1% did >80 h/week at baseline; 80% at follow-up
SF-36, mental health score, self-reported11.0 (69)
  • *Follow-up period in brackets for prospective cohort studies.

  • BDI, Beck Depression Inventory II; GHQ-12, General Health Questionnaire-12 items; HCW, Health Care Workers; SCLDS, Symptom Checklist Depression Scale.