Table 4. Quality Assessment of the Included Studies by the Newcastle-Ottawa Scale.
| Study | Selection | Comparability | Exposure | Total score |
|---|---|---|---|---|
| Baitner (1999)14) | 4 | 1 | 3 | 8 |
| Windolf (2009)15) | 4 | 1 | 3 | 8 |
| Rupprecht (2011)17) | 4 | 1 | 3 | 8 |
| Rupprecht (2011)16) | 4 | 1 | 3 | 8 |
| Hawks (2013)4) | 4 | 1 | 3 | 8 |
| Stoffel (2017)7) | 4 | 1 | 3 | 8 |
| Aminian (2007)18) | 4 | 1 | 3 | 8 |
| Samsami (2015)11) | 4 | 1 | 3 | 8 |
| Nowotarski (2012)19) | 2 | 1 | 3 | 6 |
| Gumustas (2014)6) | 2 | 1 | 3 | 6 |
| Kunapuli (2015)20) | 2 | 1 | 3 | 6 |
| Kuan (2016)9) | 2 | 1 | 3 | 6 |
| Johnson (2017)10) | 2 | 1 | 3 | 6 |
| Knobe (2018)12) | 2 | 1 | 3 | 6 |
| Noda (2015)8) | 2 | 1 | 3 | 6 |