Quality assessment of included studies by GRADE analysis.

1Insufficient information about the sequence generation process. 2 Insufficient information about the allocation concealment. 3 Blinding was not adequate. 4 I2>50%. 5 High quality: further research is very unlikely to change our confidence in the estimate of effect; moderate quality: further research is likely to have an important impact on our confidence in the estimate of effect and m ay change the estimate; low quality: further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate; very low quality: we are very uncertain about the estimate.