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The quality of the case-control studies and cohort studies
| Study | Year | Selection | Comparability | Outcome | Stars* | |
|---|---|---|---|---|---|---|
| 1 | Chen et al. | 2020 | 3 | 2 | 2 | 7 |
| 2 | Doung-ngern et al. | 2020 | 4 | 2 | 3 | 9 |
| 3 | Guo et al. | 2020 | 3 | 2 | 2 | 7 |
| 4 | Heinzerling et al. | 2020 | 2 | 2 | 2 | 6 |
| 5 | Khalil et al. | 2020 | 3 | 2 | 2 | 7 |
| 6 | Wang et al. | 2020 | 3 | 1 | 1 | 5 |
Scoring by Newcastle-Ottawa Scale.
