TABLE 4.
Study bias and quality assessment of case‐control studies using the Newcastle Ottawa Scale checklist
| Study | Cohort selection | Comparability of cases and controls on the basis of the design or analysis | Outcome ascertainment | Total rated scores | |||||
|---|---|---|---|---|---|---|---|---|---|
| Representativeness of the exposed cohort | Selection of the nonexposed cohort | Ascertainment of exposure | Demonstration that outcome of interest was Not present at start of study | Assessment of outcome | Was follow‐up long enough for outcomes to occur | Adequacy of follow‐up of cohorts | |||
| Chen B 2018 20 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 6 |
| Zeng K 2018 34 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
| He R 2017 22 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 6 |
| Yang L 2019 31 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 6 |
| Uhr K 2018 27 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 8 |
| Xu JH 2019 29 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 6 |
| Liu Z 2019 24 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 6 |
| Zhou H 2019 35 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 6 |
| Xu Y 2018 30 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 6 |
| Yang R 2019 32 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 6 |
| Wang S 2018 28 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 6 |
| Gao D 2019 21 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 6 |
| Smid M 2019 26 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 6 |