Table 3.
Results of subgroup analyses of malignant brain tumors.
| Subgroup | No. of Studies | Pooled OR (95% CI) |
Heterogeneity | |
|---|---|---|---|---|
| Research design | I2, % | p-Value | ||
| Case-control study | 3 | 1.10 (1.00–1.21) | 0 | 0.4 |
| Cohort study | 15 | 1.28 (1.05–1.56) | 0 | 0.74 |
| Subgroup difference: p = 0.1790 | ||||
| Exposure assessment method | ||||
| Blood lead (Pb) level | 6 | 1.76 (1.16–2.69) | 0 | 0.94 |
| Job information | 11 | 1.11 (1.02–1.21) | 0 | 0.62 |
| Subgroup difference: p = 0.0361 | ||||
| Cancer outcome | ||||
| Brain cancer incidence | 10 | 1.42 (1.09–1.85) | 0 | 0.89 |
| Brain cancer mortality | 7 | 1.10 (1.01–1.21) | 6 | 0.38 |
| Subgroup difference: p = 0.0381 | ||||
| Reference category | ||||
| External reference | 9 | 1.09 (0.83–1.42) | 0 | 0.93 |
| Internal reference | 9 | 1.14 (1.04–1.25) | 0 | 0.67 |
| Subgroup difference: p = 0.2594 | ||||