Figure 5

Assessment and analysis of the risk of bias in studies. (A) Six questions related to risk of bias were considered for each study (Q1-Q6). These were: Q1, Was the allocation sequence adequately generated? Q2, Was treatment allocation adequately concealed? Q3, Was blinding adequate? Q4, Was incomplete outcome data adequately addressed? Q5, Was there a selective outcome reporting? Q6, Is the study free of other biases? Answer to each question was either: no risk, high risk or uncertain. The bar chart shows, the proportion of each response for each question. Accompanying pie charts show the proportion of heterogeneity (overall Cochrane Q statistic) explained by each color coded response. The black slice in the pie shows the among-responses heterogeneity attributable to the bias being considered and is also given in percentage along side. F, Snedecor's F statistic; p, significance value for F. The F and p together indicate the statistical significance for the contribution of the bias to among-study heterogeneity. (B) Overall risk of bias as a contributor to among-study heterogeneity. The plot shows results of meta-regression of the overall risk of bias score with the log of relative risk. The risk of bias score ranged from 6 (no risk of bias) to 12 (high risk of bias). Each circle represents a trial - the diameter of a circle is proportional to the standard error in that study. Dark magenta line is the predicted regression line.