Table 4 Quality of the included studies
Study | Selection bias | Study design | Confounders | Blinding | Data collection | Drop-outs | Global rating |
|---|---|---|---|---|---|---|---|
[26] | Weak | Moderate | Weak | Weak | Strong | Strong | Weak |
[27] | Moderate | Moderate | Moderate | Weak | Strong | Strong | Moderate |
[28] | Strong | Strong | Moderate | Weak | Strong | Strong | Moderate |
[29] | Strong | Strong | Strong | Moderate | Strong | Strong | Strong |
[30] | Moderate | Moderate | Moderate | Weak | Moderate | Strong | Moderate |
[36] | Strong | Strong | Moderate | Moderate | Strong | Strong | Strong |
[31] | Moderate | Moderate | Moderate | Weak | Strong | Strong | Strong |
[33] | Moderate | Moderate | Moderate | Weak | Moderate | Moderate | Moderate |
[34] | Moderate | Moderate | Weak | Weak | Weak | Moderate | Weak |
[35] | Moderate | Moderate | Weak | Weak | Moderate | Moderate | Weak |
[37] | Moderate | Moderate | Moderate | Weak | Strong | Strong | Moderate |
[23] | Weak | Moderate | Moderate | Weak | Strong | Moderate | Weak |
[24] | Moderate | Moderate | Weak | Moderate | Moderate | Moderate | Moderate |
[25] | Moderate | Moderate | Moderate | Weak | Moderate | Strong | Moderate |
[32] | Weak | Moderate | Weak | Moderate | Moderate | Moderate | Moderate |
[38] | Moderate | Moderate | Moderate | Moderate | Strong | Strong | Strong |
[39] | Moderate | Moderate | Weak | Weak | Moderate | Strong | Weak |