Table 2.
Risk of bias of the included studies assessed by Newcastle-Ottawa Scale. Maximum number of points is nine, and a higher score means the least risk of bias.
| Study | Selection |
Comparability |
Outcome |
Total |
|||||
|---|---|---|---|---|---|---|---|---|---|
| Representativeness of the exposed cohort | Selection of the non- exposed cohort | Ascertainment of exposure | Demonstration that outcome of interest was not present at start of study | Comparability of cohorts based on the design or analysis | Assessment of outcome | Was follow-up long enough for outcomes to occur | Adequacy of follow up of cohorts | Total (9 max) | |
| Almutawa 2014 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Aoki 2010 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Bjørneboe 2010 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Calloway 2019 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Ekstrand 2006 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Ekstrand 2011a | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Ekstrand 2011b | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Ekstrand 2012 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Fuller 2007a | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Fuller 2007b | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Howard 2020 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 6 |
| Hägglund 2011 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Hägglund 2016 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Kordi 2011 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Kristenson 2013 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Kristenson 2016 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Lanzetti 2017 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |
| Meyers 2013 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Meyers 2014 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Rössler 2018 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Soligard 2012 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 9 |
| Steffen 2007 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7 |