Table 4. Assessment of risk of bias for observational study included.

Manuscript Check-list for Non-randomized studies of intervention	Roberts et al., 2005
Bias due to confounding	Yes
Bias in selection of participants into the study	Yes
Bias in classification of interventions	Yes
Bias due to deviations from intended intervention	Yes
Bias due to missing data	UNCLEAR
Bias in measurement of outcomes	UNCLEAR
Bias in selection of the reported result	UNCLEAR
Was appropriate statistical analysis used?	No