Table 2.
The associated risk of bias according to the NOS scores
| Study | Selection | Comparability | Outcome | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Representativeness of the exposed cohort | Selection of the non-exposed cohort | Ascertainment of exposure | Demonstration that outcome of interest was not present at start of study | Comparability of cohorts on the basis of the design or analysis | Assessment of outcome | Was follow-up long enough for outcomes to occur | Adequacy of follow-up of cohorts | All | |
| Kim (2020) | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 7 |
| Tajima (2020) | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 0 | 8 |
| Yang (2019) | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 0 | 8 |
| Bae (2019) | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 7 |
| Lu (2017) | 1 | 1 | 1 | 1 | 2 | 1 | 0 | 0 | 7 |
| Matsushima (2017) | 1 | 1 | 1 | 1 | 0 | 1 | 0 | 0 | 5 |
| Li (2016) | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Enomoto (2016) | 1 | 1 | 1 | 1 | 0 | 1 | 0 | 0 | 5 |
| Zhou (2013) | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 0 | 8 |
| Law (2013) | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 7 |
| Chung (2008) | 1 | 1 | 1 | 1 | 0 | 1 | 0 | 0 | 5 |
| Stipa (2008) | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
NOS Newcastle–Ottawa quality assessment Scale