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Quality assessment of included studies
| Author | Representativeness | Selection of the non exposed cohort | Ascertainment | Outcome was not present at start of study | Comparability | Assessment of outcome | Follow‐up time | Adequacy of follow‐up | Quality |
|---|---|---|---|---|---|---|---|---|---|
| Yang (12) | ⋆ | ⋆ | ⋆ | ⋆ | ⋆ | ⋆ | ⋆ | High | |
| Weinhandl (2011) | ⋆ | ⋆ | ⋆ | ⋆ | ⋆ | ⋆ | ⋆ | High | |
| Brunelli (2008) | ⋆ | ⋆ | ⋆ | ⋆ | ⋆ | ⋆ | ⋆ | High |
The star symbol means the corresponding assessment has been met.
