Background
Methods
Search strategy and data selection
Data extraction
Statistical analysis
Methodological trial characteristic | Risk of Bias judgement according to review authors | ||||||
---|---|---|---|---|---|---|---|
Total | Low | Unclear | High | ||||
N | N | % | N | % | N | % | |
Random sequence generation | 831 | 618 | 74.4 | 205 | 24.7 | 8 | 0.9 |
Allocation concealment | 925 | 541 | 58.5 | 370 | 40.0 | 14 | 1.5 |
Blinding of participants and personnel | 430 | 264 | 61.4 | 88 | 20.5 | 78 | 18.1 |
Blinding of outcome assessment | 500 | 348 | 69.6 | 136 | 27.2 | 16 | 3.2 |
Incomplete outcome data | 872 | 583 | 66.9 | 149 | 17.1 | 140 | 16.0 |
Selective reporting | 567 | 369 | 65.1 | 147 | 25.9 | 51 | 9.0 |
Dietary compliance | 234 | 119 | 50.9 | 100 | 42.7 | 15 | 6.4 |
Characteristics of meta-analyses of randomised controlled trials
Average bias associated with the methodological trial characteristics
Methodological trial characteristic (high/unclear versus low RoB judgement) | N (meta-analyses) | RRR (95% CI) | Heterogeneity (I2; τ2) | 95% PIa |
---|---|---|---|---|
Random sequence generation | ||||
Main analysis | 39 | 0.97 (0.93; 1.02) | 28%; 0.002 | 0.88; 1.08 |
Micronutrients | 23 | 0.96 (0.92; 1.00) | 2%; 0 | 0.91; 1.00 |
Fatty acids | 11 | 0.97 (0.76; 1.23) | 62%; 0.09 | 0.76; 1.23 |
Dietary approach | 3 | 0.99 (0.82; 1.20) | 0%; 0 | 0.29; 3.41 |
All-cause mortality | 11 | 0.96 (0.88; 1.04) | 19%; 0.005 | 0.80; 1.16 |
Pregnancy outcomes | 7 | 0.98 (0.90; 1.07) | 38%; 0 | 0.88; 1.10 |
Mostly subjectively assessed | 21 | 1.00 (0.87; 1.14) | 35%; 0.03 | 0.69; 1.44 |
Excluding highly correlated outcomes | 28 | 0.94 (0.85; 1.03) | 42%; 0.02 | 0.69; 1.26 |
Including only one outcome per comparison | 19 | 0.98 (0.92; 1.04) | 28%; 0.003 | 0.85; 1,12 |
Allocation concealment | ||||
Main analysis | 46 | 1.00 (0.96; 1.04) | 27%; 0.001 | 0.92; 1.08 |
Micronutrients | 26 | 1.00 (0.95; 1.06) | 33%; 0.002 | 0.90; 1.11 |
Fatty acids | 14 | 0.93 (0.83; 1.05) | 37%; 0.01 | 0.70; 1.25 |
Dietary approach | 4 | 1.05 (0.96; 1.15) | 0%; 0 | 0.85; 1.29 |
All-cause mortality | 12 | 0.97 (0.91; 1.04) | 33%; 0.003 | 0.85; 1.12 |
Pregnancy outcomes | 11 | 1.04 (0.97; 1.11) | 47%; 0 | 0.96; 1.12 |
Mostly subjectively assessed | 23 | 1.00 (0.92; 1.09) | 13%; 0 | 0.92; 1.09 |
Excluding highly correlated outcomes | 34 | 0.98 (0.93; 1.03) | 29%; 0.002 | 0.87; 1.09 |
Including only one outcome per comparison | 22 | 0.98 (0.93; 1.04) | 25%; 0.002 | 0.88; 1.09 |
Blinding of participants and personnel | ||||
Main analysis | 29 | 0.95 (0.91; 1.00) | 23%; 0 | 0.90; 1.01 |
Micronutrients | 17 | 0.95 (0.85; 1.07) | 31%; 0.004 | 0.79; 1.15 |
Fatty acids | 11 | 0.96 (0.90; 1.02) | 6%; 0 | 0.89; 1.03 |
Dietary approach | n/a | n/a | n/a | n/a |
All-cause mortality | 5 | 0.95 (0.87; 1.04) | 0%; 0 | 0.83; 1.10 |
Pregnancy outcomes | 8 | 0.84 (0.59; 1.20) | 59%; 0.14 | 0.30; 2.33 |
Mostly subjectively assessed | 16 | 0.94 (0.88; 1.01) | 10%; 0 | 0.88; 1.02 |
Excluding highly correlated outcomes | 18 | 0.95 (0.89; 1.02) | 6%; 0 | 0.88; 1.02 |
Including only one outcome per comparison | 11 | 0.96 (0.89; 1.04) | 28%; < 0.0001 | 0.88; 1.05 |
Blinding of outcome assessment | ||||
Main analysis | 28 | 0.81 (0.70; 0.94) | 26%; 0.03 | 0.54; 1.23 |
Micronutrients | 15 | 0.90 (0.77; 1.05) | 37%; 0.02 | 0.62; 1.29 |
Fatty acids | 10 | 0.62 (0.47; 0.82) | 0%; 0 | 0.45; 0.86 |
Dietary approach | 2 | 0.88 (0.39; 2.02) | 0%; 0 | n/a |
All-cause mortality | 5 | 0.83 (0.64; 1.08) | 0%; 0.02 | 0.46; 1.51 |
Pregnancy outcomes | 10 | 0.86 (0.62; 1.18) | 49%; 0.11 | 0.37; 1.98 |
Mostly subjectively assessed | 13 | 0.74 (0.59; 0.93) | 0%; 0.02 | 0.48; 1.13 |
Excluding highly correlated outcomes | 19 | 0.81 (0.67; 0.98) | 27%; 0.04 | 0.51; 1.29 |
Including only one outcome per comparison | 12 | 0.88 (0.73; 1.07) | 17%; 0.03 | 0.58; 1.35 |
Incomplete outcome data | ||||
Main analysis | 37 | 0.92 (0.88; 0.97) | 22%; 0.001 | 0.85; 1.00 |
Micronutrients | 20 | 0.92 (0.87; 0.98) | 36%; 0.001 | 0.85; 1.01 |
Fatty acids | 11 | 0.82 (0.72; 0.94) | 0%; 0 | 0.71; 0.96 |
Dietary approach | 6 | 1.00 (0.89; 1.12) | 42%; 0.001 | 0.83; 1.20 |
All-cause mortality | 11 | 0.91 (0.85: 0.98) | 0%; 0 | 0.84; 0.99 |
Pregnancy outcomes | 11 | 0.76 (0.54; 1.07) | 60%; 0.18 | 0.27; 2.14 |
Mostly subjectively assessed | 15 | 0.88 (0.78; 1.00) | 0%; 0.01 | 0.69; 1.12 |
Excluding highly correlated outcomes | 26 | 0.93 (0.88; 0.99) | 19%; 0.001 | 0.84; 1.03 |
Including only one outcome per comparison | 17 | 0.92 (0.86; 0.98) | 38%; 0.002 | 0.82; 1.03 |
Selective reporting | ||||
Main analysis | 23 | 0.97 (0.92; 1.02) | 24%; 0 | 0.92; 1.02 |
Micronutrients | 15 | 0.99 (0.92; 1.07) | 19%; 0 | 0.92; 1.07 |
Fatty acids | 5 | 0.95 (0.89; 1.02) | 63%; 0 | 0.86; 1.06 |
Dietary approach | 3 | 1.14 (0.54; 2.41) | 0%; 0 | 0.01; 144.53 |
All-cause mortality | 7 | 0.96 (0.90; 1.02) | 51%; < 0.0001 | 0.88; 1.04 |
Pregnancy outcomes | 8 | 0.99 (0.65; 1.51) | 0%; 0 | 0.59; 1.68 |
Mostly subjectively assessed | 8 | 1.05 (0.90; 1.22) | 48%; 0.02 | 0.70; 1.56 |
Excluding highly correlated outcomes | 18 | 0.98 (0.93; 1.04) | 35%; 0 | 0.92; 1.04 |
Including only one outcome per comparison | 12 | 1.00 (0.81; 1.25) | 56%; 0.07 | 0.54; 1.87 |
Dietary compliance | ||||
Main analysis | 15 | 0.95 (0.89; 1.02) | 0%; 0 | 0.88; 1.03 |
All-cause mortality | 5 | 0.95 (0.86; 1.05) | 0%; 0 | 0.81; 1.12 |
Mostly subjectively assessed | 10 | 0.96 (0.87; 1.06) | 0%; 0 | 0.85; 1.08 |
Excluding highly correlated outcomes | 10 | 0.94 (0.87; 1.03) | 0%; 0 | 0.85; 1.04 |
Including only one outcome per comparison | 6 | 0.99 (0.89; 1.09) | 0%; < 0.0001 | 0.86; 1.13 |
Trial characteristic (high/unclear versus low RoB judgement) | N (meta-analyses) | DSMD (95% CI) | Heterogeneity (I2; τ2) | 95% PIa |
---|---|---|---|---|
Random sequence generation | ||||
Main analysis | 21 | 0.01 (− 0.08; 0.09) | 28%; 0.01 | − 0.18; 0.19 |
Excluding highly correlated outcomes | 13 | − 0.01 (− 0.12; 0.09) | 36%; 0.03 | − 0.40; 0.40 |
Including only one outcome per comparison | 11 | − 0.01 (− 0.13; 0.12) | 42%; 0.01 | − 0.29; 0.28 |
Allocation concealment | ||||
Main analysis | 23 | 0.03 (− 0.07; 0.12) | 51%; 0.02 | − 0.32; 0.37 |
Excluding highly correlated outcomes | 13 | 0.02 (− 0.12; 0.17) | 62%; 0.04 | − 0.43; 0.47 |
Including only one outcome per comparison | 12 | 0.03 (− 0.12; 0.19) | 66%; 0.04 | − 0.46; 0.53 |
Blinding of participants and personnel | ||||
Main analysis | 10 | − 0.09 (− 0.17; 0.00) | 0%; 0 | − 0.19; 0.01 |
Excluding highly correlated outcomes | 5 | − 0.06 (− 0.18; 0.07) | 0%; 0 | − 0.26; 0.15 |
Including only one outcome per comparison | 5 | − 0.12 (− 0.24; 0.01) | 0%; 0 | − 0.32; 0.98 |
Blinding of outcome assessment | ||||
Main analysis | 21 | 0.07 (− 0.02; 0.16) | 33%; 0.01 | − 0.19; 0.33 |
Excluding highly correlated outcomes | 11 | 0.12 (0.00; 0.24) | 23%; 0.01 | − 0.15; 0.39 |
Including only one outcome per comparison | 10 | 0.07 (− 0.09; 0.23) | 52%; 0.03 | − 0.37; 0.51 |
Incomplete outcome data | ||||
Main analysis | 23 | − 0.05 (− 0.15; 0.06) | 58%; 0.03 | − 0.43; 0.34 |
Excluding highly correlated outcomes | 13 | − 0.08 (− 0.23; 0.06) | 61%; 0.04 | − 0.56; 0.39 |
Including only one outcome per comparison | 12 | − 0.10 (− 0.25; 0.06) | 63%; 0.04 | − 0.06; 0.41 |
Selective reporting | ||||
Main analysis | 13 | − 0.10 (− 0.18; − 0.03) | 0%; 0 | − 0.19; − 0.02 |
Excluding highly correlated outcomes | 8 | − 0.08 (− 0.18; 0.03) | 16%; 0.002 | − 0.25; 0.10 |
Including only one outcome per comparison | 8 | − 0.13 (− 0.22; − 0.03) | 5%; < 0.0001 | − 0.25; 0.00 |