Table 2

Risk of bias in included studies

StudyStudy participationStudy attritionPrognostic factor measurementOutcome measurementStudy confoundingStatistical analysis and reporting
Chung et al 201637 Low risk High risk Low riskLow riskModerate risk High risk
Oldham et al 201638 Low risk High risk Low riskLow riskModerate risk High risk
Adegunsoye et al 201739 Moderate risk High risk Low riskLow riskModerate risk High risk
Ahmad et al 201740 Low risk High risk Low riskLow riskModerate risk High risk
Collins et al 201741 Low risk High risk Low riskLow risk High risk High risk
Dai et al 201842 Low risk High risk Low riskLow risk High risk High risk
Lim et al 201943 Low risk High risk Low riskLow riskModerate risk High risk
Ito et al 201744 Low risk High risk Low riskLow riskModerate risk High risk
Mejía et al 201745 Low risk High risk Low riskLow riskModerate risk High risk
Kelly and Moua 201746 Low risk High risk Low riskLow riskModerate risk High risk
Yoshimura et al 201847 Low risk High risk Low riskLow riskModerate risk High risk
Kim et al 201948 Low risk High risk Low riskLow riskModerate risk High risk
  • Bold text indicates high risk of bias.