Quality assessment of included studies using Newcastle-Ottawa scale
| Study | Selection | Comparability | Outcome | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Representativeness of exposed cohort | Selection of non-exposed cohort | Ascertainment of exposure | Assessed outcome of interest was not present at start | Total | Risk of bias | Comparability of cohorts on basis of design or analysis | Total | Risk of bias | Assessment of outcome | Follow-up adequate for outcomes to occur | Adequate follow-up of cohorts | Total | Risk of bias | |||
| White 198711 | * | — | * | * | 3 | Medium | — | 0 | High | * | — | — | 1 | High | ||
| Pereira 19961 | * | — | * | * | 3 | Medium | — | 0 | High | * | — | — | 1 | High | ||
| Fenton 20038 | * | — | * | * | 3 | Medium | ** | 2 | Low | * | — | — | 1 | High | ||
| Chilopora 200710 | * | — | * | * | 3 | Medium | — | 0 | High | * | — | * | 2 | Medium | ||
| Hounton 20093 | * | — | * | * | 3 | Medium | * | 1 | Medium | * | — | — | 1 | High | ||
| McCord 200912 | * | — | * | * | 3 | Medium | — | 0 | High | * | — | — | 1 | High | ||