Table 2.
Results of quality assessment using the Newcastle-Ottawa Scale for case-control studies.
| Study | Selection | Comparability | Exposure | Scores | |||||
|---|---|---|---|---|---|---|---|---|---|
| Adequate definition of cases | Representativeness of the cases | Selection of controls | Definition of controls | Control for important factors | Ascertainment of exposure | Same method of ascertainment for cases and controls | Non-response rate | ||
| Chen, 2015 | ※ | ※ | - | ※ | ※※ | - | ※ | - | 6 |
| Chen, 2019 | ※ | ※ | - | ※ | ※※ | -- | ※ | - | 6 |
| Lai, 2018 | ※ | ※ | - | ※ | ※※ | - | ※ | - | 6 |
| Qiao, 2021 | ※ | ※ | - | ※ | ※ | ※ | - | 5 | |
※Scoring point.