Table 2. Quality assessment of included prospective and case-control studies.
| Prospective Studies | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Study | Exposed cohort represents average in community | Selection of the non-exposed cohort from same community | Ascertain exposure through records or structured interviews | Demonstrate that outcome not present at study start | Exposed and non-exposed matched and/or adjusted by factors | Ascertain outcome via independent blind assessment or record linkage | Follow-up long enough for outcome to occur | Loss to follow-up<20% | Overall Score |
| Alves Nogueira Fabro, 2012 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Lundstedt, 2012 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 4 |
| Rief, 2011 | 1 | 1 | 1 | 0 | 2 | 0 | 1 | 1 | 7 |
| Johannsen, 2015 | 1 | 1 | 1 | 0 | 2 | 0 | 1 | 1 | 7 |
| Juhl, 2016 | 1 | 1 | 1 | 0 | 2 | 0 | 1 | 1 | 7 |
| Lash, 2000 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| De Oliveira, 2014 | 1 | 1 | 1 | 1 | 2 | 0 | 1 | 1 | 8 |
| Meretoja, 2014 | 1 | 1 | 0 | 1 | 2 | 0 | 1 | 1 | 7 |
| Case-Control Studies | |||||||||
| Study | Case defined with independent validation | Representativeness of the cases | Selection of controls from community | Statement that controls have no history of outcome | Cases and controls matched and/or adjusted by factors | Ascertain exposure by blinded structured interview | Same method of ascertainment for cases and controls | Same response rate for both groups | Overall Score |
| Shahbazi, 2015 | 0 | 1 | 1 | 0 | 2 | 1 | 1 | 1 | 7 |
1 means study adequately fulfilled a quality criterion (2 for case-control or exposed-non exposed fully matched and adjusted), 0 means it did not. Quality scale does not imply that items are of equal relevant importance.