From: Systematic review of the relation between smokeless tobacco and cancer in Europe and North America
 |  |  |  | Heterogeneity | ||
---|---|---|---|---|---|---|
Type of ST (region)a | Adjustments/restrictionsb | Number of estimates (RR/OR ids)c | Random-effects RR/OR (95% CI) | χ2 | I2 | P(χ2) |
Any | Overall data | n = 41 (1, 2, 3, 6, 7, 11, 15, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26, 28, 29, 30, 33, 34, 35, 38, 39, 41, 42, 46, 47, 48, 49, 51, 55, 56, 58, 60, 63, 65, 73, 74, 77) | 1.79 (1.36–2.36) | 335.6 | 88.1 | < 0.001 |
 | Smoking-adjusted | n = 19 (2, 3, 6, 7, 11, 13, 18, 26, 35, 43, 48, 51, 55, 56, 58, 63, 69, 74, 77) | 1.36 (1.04–1.77) | 69.5 | 74.1 | < 0.001 |
 | Smoking and alcohol adjusted | n = 10 (2, 3, 11, 51, 55, 56, 63, 69, 74, 77) | 1.07 (0.84–1.37) | 12.5 | 28.0 | 0.186 |
 | Never smokers | n = 9 (2, 3, 10, 12, 27, 43, 48, 59, 72) | 1.72 (1.01–2.94) | 15.9 | 49.7 | 0.044 |
 | Never smokers – alcohol adjusted | n = 3 (2, 3, 12) | 1.87 (0.82–4.27) | 0.6 | 0.0 | 0.731 |
Any (USA)d | Overall data | n = 31 (1, 2, 3, 15, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26, 29, 30, 33, 34, 35, 38, 39, 41, 42, 46, 49, 51, 55, 56, 58, 65, 74) | 2.16 (1.55–3.02) | 275.8 | 89.1 | < 0.001 |
 | Smoking-adjusted | n = 12 (2, 3, 13, 18, 26, 35, 43, 51, 55, 56, 58, 74) | 1.65 (1.22–2.25) | 33.6 | 67.3 | < 0.001 |
 | Smoking and alcohol adjusted | n = 6 (2, 3, 51, 55, 56, 74) | 1.04 (0.80–1.35) | 1.8 | 0.0 | 0.875 |
 | Never smokers | n = 5 (2, 3, 27, 43, 59) | 3.33 (1.76–6.32) | 3.5 | 0.0 | 0.476 |
 | Never smokers – alcohol adjusted | n = 2 (2, 3) | 1.58 (0.52–4.81) | 0.4 | 0.0 | 0.512 |
Snuff (Scandinavia) | Overall data | n = 7 (6, 7, 11, 48, 63, 69, 77) | 0.97 (0.68–1.37) | 14.5 | 58.8 | 0.024 |
 | Smoking-adjusted | n = 7 (6, 7, 11, 48, 63, 69, 77) | 0.97 (0.68–1.37) | 14.5 | 58.8 | 0.024 |
 | Smoking and alcohol adjusted | n = 4 (11, 63, 69, 77) | 1.10 (0.64–1.90) | 10.7 | 71.9 | 0.014 |
 | Never smokers | n = 4 (10, 12, 48, 72) | 1.01 (0.71–1.45) | 2.2 | 0.0 | 0.524 |
 | Never smokers – alcohol adjusted | n = 1 (12) | 2.30 (0.67–7.92) | -- | -- | -- |
Published since 1990 | Overall data | n = 18 (1, 2, 3, 6, 7, 11, 48, 49, 51, 55, 56, 58, 60, 63, 65, 73, 74, 77) | 1.28 (0.94–1.76) | 81.7 | 79.2 | < 0.001 |
 | Smoking-adjusted | n = 14 (2, 3, 6, 7, 11, 48, 51, 55, 56, 58, 63, 69, 74, 77) | 1.00 (0.83–1.20) | 18.5 | 29.8 | 0.139 |
 | Smoking and alcohol adjusted | n = 10 (2, 3, 11, 51, 55, 56, 63, 69, 74, 77) | 1.07 (0.84–1.37) | 12.5 | 28.0 | 0.186 |
 | Never smokers | n = 7 (2, 3, 10, 12, 48, 59, 72) | 1.24 (0.80–1.90) | 7.5 | 20.1 | 0.277 |
 | Never smokers – alcohol adjusted | n = 3 (2, 3, 12) | 1.87 (0.82–4.27) | 0.6 | 0.0 | 0.731 |