Results of planned sensitivity analyses
| Model | Description | Study IDs | Model results from combining k studies | ||||
| Unadjusted | Adjusted* | ||||||
| k | ERR estimate (95% CI) | k | ERR estimate (95% CI) | ||||
| I | Full | Prefers ‘stand alone’ to pooled studies | 1–5b, 6, 8–13, 15–20 | 18 | 0.17 (0.09 to 0.26) | 23 | 0.15 (0.07 to 0.23) |
| b | Full excluding outlying study ID 2 | 1, 3–5b, 6, 8–13, 15–20 | 17 | 0.21 (0.11 to 0.33) | 22 | 0.18 (0.08 to 0.29) | |
| c | Model ‘b’ excluding outlying study ID 1 | 3–5b, 6, 8–13, 15–20 | 16 | 0.25 (0.08 to 0.46) | 20 | 0.18 (0.02 to 0.36) | |
| d | Model ‘c’ limited to mortality studies | 3, 5b, 6, 9, 11–13, 15–20 | 13 | 0.25 (0.07 to 0.46) | 16 | 0.18 (0.01 to 0.37) | |
| e | Model ‘c’ limited to occupational studies | 4, 5b, 6, 8, 9, 11–13, 15–20 | 14 | 0.24 (0.06 to 0.44) | 18 | 0.16 (0.00 to 0.35) | |
| f | Model ‘c’ limited to results from linear modelling | 3–5b, 8–13, 15–19 | 14 | 0.24 (0.06 to 0.45) | 18 | 0.15 (−0.01 to 0.33) | |
| II | Full | Prefers pooled to ‘stand alone’ studies | 1–5a, 6, 7b, 8, 10, 13, 18 | 11 | 0.16 (0.07 to 0.26) | 15 | 0.15 (0.06 to 0.24) |
| b | Full excluding study ID 2 | 1, 3–5a, 6, 7b, 8, 10, 13, 18 | 10 | 0.21 (0.09 to 0.35) | 13 | 0.19 (0.07 to 0.32) | |
| c | Model ‘b’ excluding study ID 1 | 3–5a, 6, 7b, 8, 10, 13, 18 | 9 | 0.34 (0.04 to 0.72) | 9 | NA | |
| d | Model ‘c’ limited to mortality studies | 3, 5a, 6, 7b, 13, 18 | 6 | 0.35 (0.02 to 0.79) | 7 | 0.37 (0.03 to 0.81) | |
| e | Model ‘c’ limited to occupational studies | 4, 5a, 6, 7b, 8, 13, 18 | 7 | 0.30 (−0.01 to 0.70) | 7 | NA | |
| f | Model ‘c’ limited to results from linear modelling | 3–5a, 7b, 8, 13, 18 | 8 | 0.34 (0.01 to 0.77) | 8 | NA | |
↵* Results adjusted for publication bias by trim and fill methods. The number of studies combined, k, represents the sum of the actual studies and the ‘pseudo’ studies required for the bias adjustment.
NA, not applicable.