Table 4.
Quality of bias assessment of the included studies according to Cochrane guidelines.
| First author (year) | Sequence generation | Allocation concealment | Blinding of participants, personnel, and outcome | Incomplete outcome data | Selective outcome reporting | Other potential threats to validity |
|---|---|---|---|---|---|---|
| Pan, 1997 (21) | L | L | H | L | L | L |
| Gong, 2011 (22) | L | L | H | L | L | L |
| Ramachandran, 2013 (23) | L | L | H | L | L | L |
| Nanditha, 2018 (24) | L | L | H | L | L | L |
| Lindström, 2006 (25) | L | L | H | L | L | L |
| Aro, 2019 (14) | L | L | H | L | L | L |
| Knowler, 2002 (26) | L | L | L | L | L | L |
| The Diabetes Prevention Program Research Group, 2015 (27) | L | L | H | L | L | L |
| Penn, 2009 (28) | L | L | H | L | L | L |
| Roumen, 2008 (39) | L | L | H | L | L | L |
| Davies, 2016 (29) | L | L | H | L | L | L |
| Balducci, 2006 (30) | L | L | H | L | L | L |
| Kosaka, 2005 (31) | L | L | H | L | L | L |
| Ramachandran, 2006 (32) | L | L | H | L | L | L |
| Liao, 2002 (33) | L | L | H | L | L | L |
| Lindahl, 2009 (34) | L | L | H | L | L | L |
| Saito, 2011 (35) | L | L | H | L | L | L |
| Sakane, 2011 (36) | L | L | H | L | L | L |
| Zong, 2015 (37) | L | L | U | L | L | L |
| Hellgren, 2016 (38) | L | L | U | L | L | L |
L, low risk of bias; H, high risk of bias; U, unclear risk of bias.