Table 5 Risk of bias assessment
Risk of bias by type | ||||||||
|---|---|---|---|---|---|---|---|---|
Study | Confounding | Selection | Measurement of interventions | Performance | Missing data | Measurement of outcomes | Reporting | Overall |
Chan [13] | Moderate | Low | Low | Low | Moderate | Moderate | Low | Moderate |
Christensen [9] | Moderate | Moderate | Moderate | No information | Low | Serious | Low | Serious |
Koch [14] | Moderate | Low | Low | Low | Low | Moderate | Low | Moderate |
Cazemier [15] | Serious | Serious | Serious | Low | Low | Serious | Low | Serious |
Gosselink [16] | Low | Serious | Moderate | Low | Moderate | Serious | Low | Serious |
Gardiner [18] | No information | No information | Moderate | No information | Low | Serious | No information | Serious |
Crawshaw [17] | Moderate | Serious | Serious | Low | Serious | Serious | Low | Serious |