| Author | Year | Selection | Comparability | Outcome | Total Score |
|---|
| Prospective Cohort |
| Gebhardt et al. [23], | 2006 | 2/4 | 1/2 | 3/3 | 6/9 |
| Klyne et al. [26], | 2018a | 2/4 | 2/2 | 2/3 | 6/9 |
| Sturmer et al. [28], | 2005 | 2/4 | 1/2 | 2/3 | 5/9 |
| Case-control |
| Heffner et al. [24], | 2011 | 1/4 | 2/2 | 1/3 | 4/9 |
| Klyne et al. [25], | 2017a | 4/4 | 2/2 | 1/3 | 7/9 |
| Luchting et al. [27], | 2016 | 2/4 | 2/2 | 0/3 | 4/9 |
| Wang et al. [30], | 2008 | 2/4 | 1/2 | 1/3 | 4/9 |
| Prospective Cross-sectional study |
| Wang et al. [29], | 2010 | 4/5 | 2/2 | 1/3 | 7b/10 |
- aParticipants in Klyne et al.’s 2018 study taken from the same sample as Klyne et al.’s 2017 study
- bNewcastle Ottawa Scale (NOS) cross-sectional scale is out of 10
