TABLE 2.
Risk-of-bias assessment for included studies
| Domains of bias evaluation (low, moderate, or high risk of bias)1 | ||||||
|---|---|---|---|---|---|---|
| Study category and identification | Study participants | Study attrition | Prognostic factor measurement | Outcome measurement | Study confounding | Statistical analysis and reporting |
| Protein-energy supplementation | ||||||
| Hawkesworth 2011 (Trial 1) (21) | Low | Moderate | Low | Low | Low | Low |
| Hawkesworth 2009 (54) | Low | Moderate | Low | Low | Low | Low |
| Hawkesworth 2008 (22) | Low | Moderate | Low | Low | Low | Low |
| Kinra 2008 (55) | Low | Low | Low | Low | Low | Low |
| Macleod 2013 (23) | High | Moderate | Low | Low | Low | Moderate |
| Long-chain polyunsaturated fatty acid supplementation | ||||||
| Asserhøj 2009 (39) | Moderate | Moderate | Low | Low | Low | Low |
| Brei 2016 (56) | Low | Moderate | Low | Low | Moderate | Low |
| Foster 2017 (57) | Moderate | Low | Low | Low | Moderate | Moderate |
| Gutierrez-Gomez 2017 (24) | Low | Moderate | Low | Low | Moderate | Low |
| Kerling 2019 (40) | Low | Moderate | Low | Low | Moderate | Low |
| Muhlhausler 2016 (25) | Low | Low | Low | Low | Low | Low |
| Rytter 2012 (41) | Low | Moderate | Low | Low | Low | Low |
| Rytter 2011a (26) | Low | Moderate | Low | Low | Low | Low |
| Rytter 2011b (36) | Low | Moderate | Low | Low | Low | Low |
| See 2018 (27) | Moderate | Moderate | Low | Low | Moderate | Moderate |
| Vinding et al. 2018 (58) | Low | Low | Low | Low | Low | Low |
| Single-micronutrient supplementation | ||||||
| Belizan 1997 (42) | Low | Moderate | Low | Low | Moderate | Low |
| Hawkesworth 2011 (Trial 2) (21) | Low | Moderate | Low | Low | Low | Low |
| Hiller 2007 (43) | Moderate | High | Low | Low | Moderate | Moderate |
| Palmer 2020 (59) | Low | High | Low | Low | Low | Low |
| Taylor 2015 (60) | Low | Low | Low | Low | Low | Low |
| Multiple-micronutrient supplementation | ||||||
| Ekström 2016 (Trial 1) (28) | Low | Low | Low | Low | Moderate | Moderate |
| Kumordzie 2019 (61) | Low | Low | Low | Low | Low | Low |
| Mannan 2016 (62) | Low | High | Low | Low | Low | Moderate |
| Stewart 2011 (63) | Low | Moderate | Low | Low | Low | Low |
| Stewart 2009 (64) | Low | Low | Low | Low | Low | Low |
| Infant and young child feeding, and milk supplementation | ||||||
| de Jong 2011 (44) | Low | Low | Low | Low | Moderate | Moderate |
| Forsyth 2003 (45) | Low | Moderate | High | High | High | High |
| Gruszfeld 2016 (65) | Low | High | Low | Low | Low | Low |
| Gruszfeld 2015 (37) | Low | Moderate | Low | Low | High | Moderate |
| Kennedy 2010 (46) | Low | Moderate | Low | Low | Moderate | Low |
| Kramer 2007 (66) | Low | Low | Low | Low | Low | Moderate |
| Martin 2017 (47) | Low | Low | Low | Low | Low | Low |
| Martin 2014 (29) | Low | Low | Low | Low | Low | Low |
| Martin 2013 (67) | Low | Low | Low | Low | Low | Low |
| Singhal 2010 (49) | Low | Moderate | Low | Low | Low | Low |
| Singhal 2004 (38) | Moderate | High | Low | Low | Low | Low |
| Singhal 2003 (30) | Moderate | High | Low | Low | Low | Low |
| Singhal 2002 (68) | Moderate | High | Low | Low | Low | Moderate |
| Singhal 2001 (48) | Moderate | High | Low | Low | Low | Low |
| Toftlund 2018 (31) | Moderate | Moderate | Low | Low | Moderate | Moderate |
| Totzauer 2018 (69) | Low | Moderate | Low | Low | Low | Low |
| Weber 2014 (50) | Low | Moderate | Low | Low | Low | Low |
| Williams 2012 (32) | Low | Moderate | Low | Low | Low | Low |
| Dietary counseling | ||||||
| Costa 2017 (33) | Low | Moderate | Low | Low | Low | Low |
| Hakanen 2006 (70) | Low | Moderate | Low | Low | Moderate | Low |
| Lehtovirta 2018 (71) | Low | Moderate | Low | Low | Low | Moderate |
| Nupponen 2015 (72) | Low | Moderate | Low | Low | Moderate | Low |
| Pahkala 2020 (34) | Low | Moderate | Low | Low | Moderate | Low |
| Pahkala 2013 (73) | Low | Moderate | Low | Low | Moderate | Low |
| Raitakari 2005 (74) | Low | Moderate | Low | Low | Moderate | Moderate |
| Other interventions | ||||||
| Ekström 2016 (Trial 2) (28) | Low | Low | Low | Low | Moderate | Moderate |
| Luoto 2010 (75) | Moderate | Low | Low | Low | Moderate | Low |
| Videhult 2015a (35) | Low | Low | Low | Low | Moderate | Moderate |
| Videhult 2015b (76) | Low | Low | Low | Low | Moderate | Low |
Bias assessment followed specific criteria by each domain:
1) Study participants: High bias—the relation between predictor and outcome is very likely to be different for participants and eligible nonparticipants. Moderate bias—the relation could be different. Low bias—the relation is unlikely to be different.
2) Study attrition: High bias—the relation between predictor and outcome is very likely to be different for completing and noncompleting participants. Moderate bias—the relation could be different. Low bias—the relation is unlikely to be different.
3) Prognostic factor measurement: High bias—the measurement of the predictor is very likely to be different for different levels of the outcome of interest. Moderate bias—the measurement could be different. Low bias—the measurement is unlikely to be different.
4) Outcome measurement: High bias—the measurement of the outcome is very likely to be different related to the baseline level of the predictor. Moderate bias—the measurement could be different. Low bias—the measurement is unlikely to be different.
5) Study confounding: High bias—the observed effect of the predictor on the outcome is very likely to be distorted by another factor related to the predictor and outcome. Moderate bias—the effect could be distorted. Low bias—the effect is unlikely to be distorted.
6) Statistical analysis and reporting: High bias—the reported results are very likely to be spurious or biased related to analysis or reporting. Moderate bias–could be spurious or biased. Low bias—unlikely to be spurious or biased.