Table 3. Risk of Bias Among Observational Studies.
| Source | Study aspects scored for risk of biasa | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Focus | Cohort selection | Exposure measurement | Outcome measurement | Confounding | Follow-up | Results | Practice implication | |||||
| Complete | Accurate | Believable | Applicable | Fit | ||||||||
| Bardes et al,16 2017 | Low | Low | Low | Low | Some concerns | Some concerns | Low | Some concerns | Some concerns | Low | Low | Some concerns |
| Boutonnet et al,17 2018 | Low | Low | High | Low | Low | Low | Low | Low | Low | Low | Low | Low |
| Chan et al,18 2019 | Low | Low | Low | Low | Low | Low | Low | Low | Low | Low | Low | Low |
| Cole et al,19 2015 | Low | Low | Low | Low | Low | Some | Low | Some concerns | Some concerns | Low | Low | Some concerns |
| Dixon et al,20 2019 | Low | Low | Low | Low | Some concerns | Some concerns | Low | Some concerns | Some concerns | Low | Low | Low |
| El-Menyar et al,21 2020 | Low | Low | Low | Low | Low | Some concerns | Low | Some concerns | Low | Low | Low | Low |
| Glover et al,22 2019 | High | Low | High | Low | High | Low | Low | Some concerns | Some concerns | Low | Low | Low |
| Harvin et al,23 2015 | Low | Low | High | Low | High | Low | Low | Low | Some concerns | Low | Low | Low |
| Howard et al,24 2017 | Low | Low | High | Low | Low | Low | Low | Some concerns | Some concerns | High | Low | Some concerns |
| Johnston et al,25 2018 | Low | Low | High | Low | High | Low | Low | Low | Some concerns | High | High | Low |
| Khan et al,26 2018 | Low | Low | High | Low | Low | Low | Low | Some concerns | Low | Low | Low | Low |
| Lewis et al,27 2016 | Low | Low | High | Low | High | Some | Low | Some concerns | High | High | Low | Some |
| Luehr et al,28 2017 | Low | Low | High | Some | High | Low | Low | Some concerns | Low | Low | High | Low |
| Moore et al,29 2017 | Low | Low | High | Low | High | Low | Low | Low | High | Low | Low | High |
| Morrison et al,30 2012 | Low | Low | Low | Low | High | Low | Low | Low | Some concerns | Low | Low | Low |
| Morrison et al,31 2013 | Low | Low | Low | Low | Low | Low | Low | Low | Low | High | Low | Low |
| Morte et al,32 2019 | Low | Low | Low | Low | Low | Low | Low | Low | Low | High | Low | Low |
| Myers et al,33 2019 | Low | Low | High | Low | Low | Some concerns | Low | Low | Some concerns | Low | High | Some concerns |
| Neeki et al,34 2018 | Low | Low | Low | Low | Low | Low | Low | Low | Low | Some concerns | Low | Some concerns |
| Neeki et al,35 2020 | Low | Low | Low | Low | Low | Low | Low | Low | Low | Some concerns | Low | Some concerns |
| Shiraishi et al,36 2017 | Low | Low | High | Low | Low | Low | Low | Low | Low | Some concerns | Low | Low |
| Swendsen et al,37 2013 | Low | Low | Some | Low | High | Low | Low | Low | Some concerns | Low | Low | Some concerns |
| Valle et al,38 2014 | Low | Low | Low | High | Low | Some concerns | Low | Low | Some concerns | Some concerns | High | Some concerns |
| Wafaisade et al,39 2016 | Low | Low | High | Low | Low | Low | Low | Low | Low | Low | Low | Low |
| Walker et al,40 2020 | Low | High | High | Low | High | Low | Low | Some concerns | Some concerns | High | High | Some concerns |
Assessed using the Critical Appraisal Skills Programme.7 Each included study was scored on 12 aspects (from left to right): (1) whether the study addressed a clearly focused issue; (2) whether the cohort was chosen in an acceptable way; (3) whether the exposure was precisely measured to reduce bias; (4) whether the outcome was precisely measured to reduce bias; (5) whether the authors identified all significant confounding factors and whether they considered confounding factors in the design or analysis; (6) whether the follow-up of participants was complete and long enough; (7) whether the results of this study were complete; (8) whether the results were accurate; (9) whether the results were believable; (10) whether the results could be applied to local population; (11) whether the results fit with other available evidence; and (12) whether this study provided implications for practice.