Number of risk estimates | sRR | 95% CI | Heterogeneity measures | ||||
I2 (%) | P value | Q | P value | ||||
Exposure assessment method | 3.28 | 0.35 | |||||
Group-level | 13 | 1.09 | 1.00 to 1.20 | 92 | <0.01 | ||
Self-reported exposure | 5 | 1.35 | 0.95 to 1.94 | 76 | <0.01 | ||
Expert-level | 8 | 1.41 | 0.99 to 2.01 | 79 | <0.01 | ||
Biomonitoring | 1 | 1.32 | 0.75 to 2.33 | . | . | ||
Study design | 7.59 | <0.02 | |||||
Cohort (prospective) | 5 | 1.08 | 1.03 to 1.14 | 64 | <0.01 | ||
Cohort (retrospective) | 8 | 1.09 | 0.90 to 1.31 | 95 | <0.01 | ||
Case–control | 12 | 1.63 | 1.22 to 2.18 | 79 | <0.01 | ||
Publication year period | 0.01 | 0.93 | |||||
1995–2006 | 14 | 1.12 | 0.94 to 1.35 | 92 | <0.01 | ||
2007–2019 | 13 | 1.11 | 1.04 to 1.19 | 77 | <0.01 | ||
Geographic region | 9.15 | <0.01 | |||||
Europe | 12 | 1.03 | 0.96 to 1.11 | 66 | <0.01 | ||
North America | 13 | 1.28 | 1.13 to 1.45 | 92 | <0.01 | ||
Other | 2 | 2.17 | 0.42 to 11.4 | 86 | <0.01 | ||
Case–control studies only | |||||||
Exposure assessment method | 1.15 | 0.56 | |||||
Group-level | 1 | 2.37 | 1.22 to 4.61 | . | . | ||
Self-reported exposure | 4 | 1.53 | 0.89 to 2.62 | 68 | 0.02 | ||
Expert-level | 7 | 1.63 | 1.11 to 2.40 | 79 | <0.01 | ||
Exposure assessment method during publication year periods | |||||||
1995–2006 | |||||||
Exposure assessment method | 0.53 | 0.91 | |||||
Group-level | 7 | 1.16 | 0.87 to 1.55 | 95 | <0.01 | ||
Self-reported exposure | 2 | 1.02 | 0.45 to 2.33 | 67 | 0.08 | ||
Expert-level | 4 | 1.04 | 0.69 to 1.57 | 70 | 0.02 | ||
Biomonitoring | 1 | 1.32 | 0.75 to 2.33 | . | . | ||
2007–2019 | |||||||
Exposure assessment method | 5.8 | 0.05 | |||||
Group-level | 6 | 1.08 | 1.02 to 1.14 | 73 | <0.01 | ||
Self-reported exposure | 3 | 1.57 | 0.96 to 2.56 | 85 | <0.01 | ||
Expert-level | 4 | 2.00 | 1.07 to 3.75 | 76 | <0.01 |
I2=percentage of variation across studies due to heterogeneity
Q=Cochran’s Q.
sRR, summary risk ratio.