Figure 5.

(a) Risk of bias traffic light plot. D1 Inclusion criteria clear, D2 Subjects and setting clear, D3 Exposure measured in valid way, D4 Objective, standardized criteria for the condition, D5 Confounding factor identified, D6 Strategy to deal with confounding factors, D7 Outcomes measurement valid and reliable, D8 Statistical analysis appropriate. Judgement: High, moderate, low and (b) Risk of bias summary plot (unweighted). D1 Inclusion criteria clear, D2 Subjects and setting clear, D3 Exposure measured in valid way, D4 Objective, standardized criteria for the condition, D5 Confounding factors identified, D6 Strategy to deal with confounding factors, D7 Outcomes measurement valid and reliable, D8 Statistical analysis appropriate. Judgement: High, moderate, low.