Table 5. Study Risk of Bias.
| Study | Random Sequence Generation (selection bias) | Allocation concealment (selection bias) | Blinding participants and personnel (performance bias) | Blinding of outcome assessment (detection bias) | Incomplete outcome data (attrition bias) | Selective reporting (reporting bias) | Other bias |
| Bales et al. (2012) [123] | Low risk | NR | High risk | NR | High risk | Low risk | High risk |
| Brandon & Elliott-Lloyd (2006) [107] | Unclear | NR | High risk | NR | High risk | Low risk | High risk |
| Broeder et al. (1992) [108] | Unclear | NR | High risk | NR | High risk | Low risk | High risk |
| Bryner et al. (1997) [125] | Unclear | NR | High risk | NR | High risk | Low risk | High risk |
| Church et al. (2009) [16] | Unclear | NR | High risk | NR | High risk | Low risk | High risk |
| Cox et al. (2010) [124] | Low risk | NR | High risk | NR | High risk | Low risk | High risk |
| Cox et al.(2003) [129] | Unclear | NR | High risk | NR | Low risk | Low risk | High risk |
| Donnelly et al. (2003) [9] | Low risk | NR | High risk | NR | High risk. | Low risk | High risk |
| Donnelly et al. (2000) [128] | Unclear | NR | High risk | NR | Low risk | Low risk | High risk |
| Foster-Schubert et al. (2012) [110] | Low risk | NR | High risk | Low risk | Low risk | Low risk | High risk |
| Grediagin et al. (1995) [126] | Unclear | NR | High risk | NR | High risk | Low risk | High risk |
| Jakicic et al. (2011) [122] | Unclear | NR | High risk | NR | Low risk | Low risk | High risk |
| Kirkwood et al. (2007) [111] | Unclear | NR | High risk | NR | High risk | Low risk | High risk |
| Miyashita et al. (2010) [127] | High risk | NR | High risk | NR | Low risk | Low risk | High risk |
| Nieman et al. (1990) [112] | Unclear | NR | High risk | NR | Low risk | Low risk | High risk |
| Nordby et al. (2012) [113] | Low risk | NR | High risk | High risk | Low risk | Low risk | High risk |
| Pritchard et al. (1997) [114] | Unclear | NR | High risk | NR | High risk | Low risk | High risk |
| Ready et al. (1995) [115] | Unclear | NR | High risk | NR | High risk | Low risk | High risk |
| Ready et al. (1996) [116] | Unclear | NR | High risk | NR | High risk | Low risk | High risk |
| Reseland et al. (2001) [117] | Unclear | NR | High risk | NR | NR | Low risk | High risk |
| Rosenkilde et al. (2012) [121] | Low risk | NR | Low risk | Low risk | Low risk | Low risk | High risk |
| Shaw et al. (2010) [118] | Unclear | NR | High risk | NR | Low risk | Low risk | High risk |
| Van Etten et al. (1997) [119] | High risk | NR | High risk | NR | Low risk | Low risk | High risk |
| Washburn et al. (2012) [120] | Unclear | NR | High risk | NR | Low risk | Low risk | High risk |
Note. NR = Not Reported.