Table 2.
Quality appraisal of the ten studies included according to Newcastle Ottawa Scale.
| Study author, Year | Design | Selection 1 | Selection 2 | Selection 3 | Selection 4 | Comparability 1 | Exposure/Outcome 1 | Exposure/Outcome 2 | Exposure/Outcome 3 | Total |
|---|---|---|---|---|---|---|---|---|---|---|
| Crowley et al. (2011) | Case control | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 0 | 5 |
| Fagioli et al. (1991) | Cohort | 1 | NA | 1 | 0 | NA | 1 | 1 | 1 | 5 |
| Johnson et al. (2020) | Cohort | 0 | NA | 1 | 0 | NA | 1 | 1 | 0 | 2 |
| Khan et al. (2017) | Case control | 1 | 1 | 0 | 1 | 2 | 1 | 1 | 1 | 6 |
| Mandrell et al. (2012) | Cohort | 1 | NA | 1 | 0 | NA | 1 | 0 | 1 | 5 |
| Manley et al. (2012) | Cohort | 1 | NA | 1 | 0 | NA | 1 | 1 | 1 | 5 |
| Müller et al. (2006) | Cohort | 1 | NA | 1 | 0 | NA | 1 | 0 | 1 | 5 |
| O'Gorman et al. (2010) | Case control | 1 | 1 | 0 | 1 | 2 | 1 | 1 | 1 | 7 |
| Pickering et al. (2021) | Cohort | 1 | NA | 1 | 0 | 2 | 0 | 1 | 1 | 6 |
| Pilotto et al. (2019) | Cohort | 1 | NA | 0 | 0 | NA | 1 | 1 | 0 | 2 |
| Rosen and Brand (2011) | Cohort | 1 | NA | 1 | 0 | NA | 1 | 0 | 0 | 4 |
| Mean | 4,7 |
Exposure was related to case-control studies, whereas outcome was related to cohort studies. The questions related in every column refer to the Newcastle Ottawa Scale. Not assessed (NA) is noted when there was no comparison group (Selection 1 = “Adequate case definition/Representativeness of cohort”, Selection 2 = “Representativeness of cases/Selection of non-exposed cohort”, Selection 3 = “Selection of controls/Ascertainment of exposure”, Selection 4 = “Definition of controls/Outcome of interest”, Comparability 1 = “Comparability of cases and controls/cohorts”, Exposure/Outcome 1 = “Ascertainment of exposure/Assessment of outcome”, Exposure/Outcome 2 = “Method of ascertainment/Long enough follow-up”, Exposure/Outcome 3 = “Non-response rate/Adequacy of follow-up”).