Table 1

Summary of the methodological quality assessment for each study using the Hoy et al19 risk of bias tool

Asghar et al161111000004
Balbinot et al380011000002
Barr et al390011000002
Bongaerts et al241010000002
Callaghan et al290111000003
Callaghan et al320000000011
De Neeling et al201001000002
Dimova et al251011000003
Dyck et al140001000001
Franklin et al280000000000
Fujimoto et al121011000003
Fujimoto et al131011000003
Gabriel et al371001000002
Herman et al400001000001
Kannan et al410111000003
Kopf et al271110000003
Kurisu et al360011000002
Lee et al110110000002
Lin et al300001000001
Liu et al331011000003
Lu et al310111000003
Németh et al260011000002
Oohashi et al350011001003
Saadi et al420011000002
Sahin et al430111000003
Zeng et al341011000003
Ziegler et al211001000002
Ziegler et al100001000002
Ziegler et al231001000002
  • Please see online supplemental appendix 2 for full tool. Q1: Was the study’s target population a close representation of the national population in relation to relevant variables, for example, age, sex, occupation? Q2: Was the sampling frame a true or close representation of the target population? Q3: Was some form of random selection used to select the sample, or was a census undertaken? Q4: Was the likelihood of non-response bias minimal? Q5: Were data collected directly from the subjects (as opposed to a proxy)? Q6: Was an acceptable case definition used in the study? Q7: Was the study instrument that measured the parameter of interest shown to have reliability and validity? Q8: Was the same mode of data collection used for all subjects? Q9: Were the numerator(s) and denominator(s) for the parameter of interest appropriate? Overall risk of bias score: 0–3=low risk, 4–6=moderate risk, 7–9=high risk.