| Study (year) | ||
---|---|---|---|
Sang-Mok Kim (2014) | Chao-Wei Tu (2014) | Qirui Ding (2017) | |
Selection | |||
 Representativeness of the exposed cohort | * | * | * |
 Ascertainment of exposure | * | * | * |
 Outcome not present at the start of the study | * | * | * |
Comparability | Â | Â | Â |
 Comorbidities | * |  |  |
 Other factors | * | * | * |
Outcome | |||
 Assessment of the outcome | * | * | * |
 Follow-up long enough for the outcome to occur | * | * | * |
 Adequacy of the follow-up | * | * | * |
Total | 8 | 7 | 7 |