Table 4.
Quality assessment of the studies included in the review
| Authors, year | Design and materials | Consideration of potential confounders | Measurement of outcome | Measurement of exposure | Data presentation and statistical analysis | Quality assessment score | Total score |
| Chodick, 2008 | 2 | 3 | 1 | 2 | 3 | 11 | +++ |
| Milacic, 2009 | 1 | 1 | 3 | 2 | 2 | 9 | ++ |
| Ciraj-bjelac, 2010 | 2 | 1 | 3 | 2 | 2 | 10 | ++ |
| Vano, 2010 | 2 | 1 | 3 | 2 | 2 | 10 | ++ |
| Yuan, 2010 | 1 | 1 | 1 | 1 | 1 | 5 | + |
| Mrena, 2011 | 2 | 3 | 3 | 2 | 2 | 12 | +++ |
| Ciraj-bjelac, 2012 | 2 | 1 | 3 | 2 | 1 | 9 | ++ |
| Jacob, 2013 | 2 | 3 | 3 | 2 | 3 | 13 | +++ |
| Vano, 2013 | 2 | 1 | 3 | 3 | 2 | 11 | +++ |
| Auvinen, 2015 | 2 | 1 | 3 | 2 | 2 | 10 | ++ |
| Bitarafan Rajabi, 2015 | 2 | 1 | 2 | 2 | 2 | 9 | ++ |
| Negrone, 2016 | 1 | 2 | 1 | 3 | 1 | 8 | ++ |
| Bernier, 2017 | 2 | 3 | 1 | 2 | 2 | 10 | ++ |
| Matsubara, 2017 | 2 | 1 | 2 | 2 | 2 | 9 | ++ |
| Barbosa, 2018 | 2 | 2 | 3 | 1 | 2 | 10 | ++ |
| Coppeta, 2018 | 1 | 1 | 3 | 3 | 2 | 10 | ++ |
| Little, 2018 | 3 | 3 | 1 | 2 | 3 | 12 | +++ |
| Domienik-Andrzejewska, 2019 | 2 | 3 | 3 | 2 | 2 | 12 | +++ |
| Scheidemann-Wesp, 2019 | 2 | 1 | 3 | 2 | 2 | 10 | ++ |
| Velazquez-Kronen, 2019 | 3 | 2 | 1 | 2 | 3 | 11 | +++ |
| Little, 2020 | 3 | 3 | 1 | 2 | 3 | 13 | +++ |