“…Eighteen trials were randomized controlled trials, 20 – 22 , 28 – 30 , 34 – 36 , 39 , 41 – 44 , 46 – 49 whereas 12 were quasi-randomized trials ( Box 2 ). 23 – 27 , 31 – 33 , 37 , 38 , 40 , 45 There was a low risk of bias in seven trials (all randomized controlled trials), 36 , 41 , 42 , 44 , 46 – 48 some concern about bias in eight, 20 , 29 , 35 , 39 , 40 , 43 , 45 , 49 and a high risk of bias in 15. 21 – 28 , 30 – 34 , 37 , 38 Details of our findings on bias are available from the online repository.…”