| Internal validity | External validity | ||||||||
| Author and year | Selection bias (representative: yes/no) | Attrition bias (adequate: yes/no) | Detection bias (blind: yes/no) | Confounding (adjustment for other factors: yes/no | Reporting bias (well defined: yes/no) [study group] | Reporting bias (well defined: yes/no) [follow‐up] | Reporting bias (well defined: yes/no) [outcome] | Analyses (well defined: yes/no) | Overall risk of bias |
| Arima 2020 | yes | yes | unclear | unclear | yes | yes | yes | yes | Moderate |
| Cowling 2020 | yes | yes | unclear | unclear | yes | yes | yes | no | Serious |
| Lee 2020 | yes | yes | unclear | unclear | yes | yes | yes | yes | Moderate |
| Lytras 2020 | yes | yes | unclear | unclear | yes | yes | yes | yes | Moderate |
| Pang 2003 | yes | yes | unclear | yes | yes | yes | yes | yes | Moderate |
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