“…Whilst 23 studies had a low risk of bias, 11 , 23 , 24 , 28 , 32 , 33 , 37 , 46 , 48 , 51 , 54 , 57 , 58 , 59 , 61 , 62 , 65 , 66 , 67 , 70 , 73 , 75 , 76 21 had some concerns 8 , 10 , 22 , 27 , 29 , 30 , 31 , 34 , 38 , 42 , 44 , 45 , 49 , 52 , 55 , 60 , 64 , 68 , 69 , 72 , 74 and 13 had a high risk of overall bias. 25 , 26 , 35 , 36 , 39 , 40 , 41 , 43 , 47 , 50 , 56 , 63 , 71 The risk of bias of one study could not be assessed as only an abstract was available.…”