TABLE 2.
Robustness of evidence grading for the dose–response meta-analyses of cohort studies associating tea intake and risk of cancer1
| Studies, n | Cases, n | Summary RR (95% CI) | Random-effects, P value | Egger's test3 | Excess significance4 | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cancer type | Fixed effects | Random effects | Largest study | I 2 (95% CI)2 | P for Q | (95% PI) | O | E | P 5 | Evidence | ||||
| Black tea | ||||||||||||||
| Breast cancer | 5 | 7289 | 1.04 (1.00, 1.08) | 1.02 (0.95, 1.11) | 1.08 (1.02, 1.15) | 0.56 | 57.0 (0, 99.8) | 0.054 | (0.89, 1.18) | 0.841 | 1 | 1.426 | NA | NS |
| Colorectal cancer | 2 | 1495 | 0.99 (0.93, 1.04) | 0.99 (0.93, 1.04) | 0.99 (0.94, 1.05) | 0.626 | 0 | 0.609 | (0.93, 1.04) | 0.609 | 0 | 0.132 | NA | NS |
| Gastric cancer | 3 | 1059 | 0.99 (0.90, 1.09) | 1.01 (0.85, 1.19) | 0.98 (0.89, 1.08) | 0.939 | 5.4 (0, 97.7) | 0.347 | (0.81, 1.25) | 0.35 | 0 | 0.411 | NA | NS |
| Lung cancer | 2 | 2250 | 0.99 (0.94, 1.04) | 0.97 (0.89, 1.06) | 1.01 (0.95, 1.07) | 0.556 | 57.7 | 0.124 | (0.85, 1.11) | 0.124 | 0 | 0.477 | NA | NS |
| Nonmelanoma skin cancer | 3 | 1128 | 0.99 (0.95, 1.04) | 0.97 (0.86, 1.08) | 0.99 (0.93, 1.05) | 0.535 | 74.0 (9.4, 99.8) | 0.021 | (0.79, 1.17) | 0.048 | 1 | 1 | 1 | NS |
| Prostate cancer | 3 | 921 | 0.98 (0.84, 1.15) | 0.90 (0.64, 1.26) | 1.13 (0.93, 1.38) | 0.546 | 67.5 (0, 98.7) | 0.046 | (0.51, 1.61) | 0.086 | 1 | 1.04 | NA | NS |
| Green tea | ||||||||||||||
| All cancers | 3 | 4453 | 0.99 (0.98, 1.01) | 0.99 (0.96, 1.01) | 1.00 (0.98, 1.01) | 0.278 | 45.2 (0, 98.2) | 0.161 | (0.95, 1.03) | 0.083 | 1 | 0.671 | 0.649 | NS |
| Bladder cancer | 3 | 328 | 1.01 (0.95, 1.07) | 1.03 (0.93, 1.14) | 0.96 (0.88, 1.04) | 0.597 | 62.3 (0, 99.2) | 0.07 | (0.87, 1.22) | 0.022 | 1 | 0.979 | 0.979 | NS |
| Breast cancer | 6 | 4887 | 0.99 (0.96, 1.02) | 0.98 (0.92, 1.03) | 1.01 (0.96, 1.05) | 0.374 | 58.8 (0, 97.0) | 0.033 | (0.87, 1.09) | 0.087 | 1 | 1.413 | NA | NS |
| Colon cancer | 7 | 3415 | 1.00 (0.98, 1.03) | 1.00 (0.98, 1.03) | 1.00 (0.95, 1.05) | 0.802 | 19.0 (0, 88.7) | 0.285 | (0.96, 1.04) | 0.908 | 1 | 1.233 | NA | NS |
| Colorectal cancer | 8 | 4676 | 1.00 (0.98, 1.02) | 1.00 (0.97, 1.03) | 1.01 (0.97, 1.05) | 0.921 | 38.9 (0, 97.3) | 0.12 | (0.94, 1.06) | 0.412 | 1 | 1.744 | NA | NS |
| Esophageal cancer | 2 | 78 | 1.11 (0.99, 1.24) | 1.11 (0.99, 1.24) | 1.08 (0.93, 1.26) | 0.073 | 0 | 0.592 | (0.99, 1.24) | 0.592 | 0 | 0.16 | NA | NS |
| Gallbladder cancer | 2 | 238 | 0.98 (0.92, 1.04) | 0.99 (0.90, 1.09) | 0.95 (0.88, 1.02) | 0.867 | 57.6 | 0.124 | (0.86, 1.14) | 0.124 | 0 | 0.52 | NA | NS |
| Gastric cancer | 4 | 4965 | 1.00 (0.98, 1.01) | 1.00 (0.96, 1.03) | 1.01 (0.98, 1.04) | 0.83 | 62.8 (0, 99.6) | 0.045 | (0.94, 1.06) | 0.166 | 1 | 1.309 | NA | NS |
| Liver cancer | 5 | 1064 | 0.98 (0.95, 1.01) | 0.98 (0.94, 1.03) | 0.98 (0.93, 1.04) | 0.451 | 37.5 (0, 93.3) | 0.171 | (0.91, 1.06) | 0.179 | 1 | 1.011 | NA | NS |
| Lung cancer | 3 | 2224 | 0.99 (0.96, 1.03) | 0.99 (0.95, 1.04) | 1.03 (0.97, 1.08) | 0.716 | 38.4 (0, 98.1) | 0.197 | (0.93, 1.06) | 0.498 | 0 | 0.975 | NA | NS |
| Lymphoid neoplasm | 3 | 749 | 0.95 (0.92, 0.99) | 0.95 (0.92, 0.99) | 0.97 (0.92, 1.02) | 0.017 | 3.4 (0, 98.0) | 0.355 | (0.92, 0.99) | 0.207 | 1 | 0.486 | 0.421 | Weak |
| Myeloid leukemia | 2 | 133 | 0.98 (0.90, 1.08) | 0.97 (0.83, 1.13) | 1.04 (0.93, 1.17) | 0.691 | 61.6 | 0.106 | (0.77, 1.22) | 0.106 | 0 | 0.578 | NA | NS |
| Myeloid neoplasm | 2 | 131 | 0.97 (0.89, 1.06) | 0.97 (0.89, 1.06) | 0.97 (0.87, 1.09) | 0.506 | 0 | 1 | (0.89, 1.06) | 1 | 0 | 0.1 | NA | NS |
| Pancreatic cancer | 3 | 647 | 1.02 (0.98, 1.05) | 1.02 (0.98, 1.05) | 1.02 (0.97, 1.07) | 0.432 | 0 (0, 97.8) | 0.514 | (0.98, 1.05) | 0.37 | 0 | 0.319 | NA | NS |
| Prostate cancer | 4 | 1008 | 0.99 (0.95, 1.03) | 0.99 (0.95, 1.03) | 0.98 (0.93, 1.03) | 0.536 | 0 (0, 99.2) | 0.497 | (0.95, 1.03) | 0.178 | 0 | 0.499 | NA | NS |
| Rectal cancer | 7 | 1830 | 1.00 (0.96, 1.03) | 1.00 (0.96, 1.03) | 0.97 (0.91, 1.04) | 0.848 | 0 (0, 77.1) | 0.674 | (0.96, 1.03) | 0.417 | 0 | 1.123 | NA | NS |
| Thyroid cancer | 2 | 159 | 1.00 (0.92, 1.08) | 1.00 (0.92, 1.08) | 1.01 (0.93, 1.10) | 0.976 | 0 | 0.509 | (0.92, 1.08) | 0.509 | 0 | 0.161 | NA | NS |
| Tea | ||||||||||||||
| All cancers | 4 | 28,928 | 1.02 (1.01, 1.03) | 1.01 (0.98, 1.04) | 1.05 (1.03, 1.07) | 0.603 | 82.8 (44.3, 99.0) | 0.001 | (0.94, 1.08) | 0.016 | 1 | 2.678 | NA | NS |
| Bladder cancer | 5 | 1513 | 0.95 (0.91, 0.98) | 0.95 (0.91, 0.99) | 0.94 (0.89, 0.99) | 0.009 | 3.3 (0, 98.4) | 0.388 | (0.90, 0.99) | 0.139 | 1 | 0.76 | 0.765 | Weak |
| Breast cancer | 14 | 48,106 | 1.00 (0.99, 1.01) | 1.00 (0.99, 1.01) | 0.99 (0.98, 1.01) | 0.831 | 17.5 (0, 79.5) | 0.262 | (0.98, 1.03) | 0.167 | 2 | 2.739 | NA | NS |
| Cervical cancer | 2 | 22,704 | 1.03 (0.93, 1.13) | 1.03 (0.93, 1.13) | 1.03 (0.93, 1.14) | 0.611 | 0 (0, 99.2) | 0.724 | (0.93, 1.13) | 0.724 | 0 | 0.115 | NA | NS |
| Colon cancer | 14 | 19,384 | 1.00 (0.99, 1.01) | 0.99 (0.96, 1.01) | 1.02 (1.00, 1.04) | 0.357 | 42.1 (0, 95.3) | 0.049 | (0.93, 1.05) | 0.005 | 2 | 3.569 | NA | NS |
| Colorectal cancer | 9 | 38,603 | 1.00 (0.98, 1.01) | 1.00 (0.98, 1.01) | 1.00 (0.98, 1.02) | 0.624 | 0 (0, 87.1) | 0.507 | (0.98, 1.01) | 0.54 | 0 | 1.356 | NA | NS |
| Endometrial cancer | 7 | 5711 | 1.00 (0.99, 1.01) | 1.00 (0.99, 1.01) | 1.00 (0.99, 1.01) | 0.822 | 0 (0, 88.8) | 0.474 | (0.99, 1.01) | 0.548 | 1 | 1.012 | NA | NS |
| Esophageal cancer | 2 | 445 | 0.94 (0.83, 1.06) | 0.94 (0.81, 1.08) | 0.87 (0.73, 1.04) | 0.383 | 26.2 | 0.244 | (0.78, 1.12) | 0.244 | 0 | 0.425 | NA | NS |
| Gastric and esophageal cancer | 2 | 391 | 0.85 (0.73, 0.99) | 0.85 (0.73, 0.99) | 0.87 (0.74, 1.02) | 0.034 | 0 | 0.444 | (0.73, 0.99) | 0.444 | 0 | 0.18 | NA | Weak |
| Gastric cancer | 4 | 23,734 | 0.99 (0.95, 1.02) | 0.98 (0.94, 1.03) | 1.02 (0.96, 1.07) | 0.456 | 22.5 (0, 95.9) | 0.276 | (0.92, 1.05) | 0.332 | 0 | 1.036 | NA | NS |
| Glioma | 6 | 2386 | 0.98 (0.95, 1.01) | 0.98 (0.94, 1.02) | 0.95 (0.9, 1.00) | 0.399 | 35.4 (0, 93.2) | 0.171 | (0.91, 1.06) | 0.88 | 2 | 1.643 | 0.744 | NS |
| Kidney cancer | 3 | 2172 | 0.99 (0.96, 1.01) | 0.98 (0.94, 1.02) | 1.00 (0.97, 1.03) | 0.338 | 32.8 (0, 97.6) | 0.226 | (0.93, 1.04) | 0.237 | 1 | 0.593 | 0.555 | NS |
| Liver cancer | 4 | 23,168 | 0.93 (0.89, 0.98) | 0.92 (0.85, 1.00) | 0.96 (0.91, 1.03) | 0.052 | 30.7 (0, 97.8) | 0.228 | (0.82, 1.04) | 0.85 | 1 | 0.831 | 0.835 | NS |
| Lung cancer | 7 | 24,806 | 1.05 (1.03, 1.08) | 1.03 (0.97, 1.10) | 1.10 (1.06, 1.14) | 0.301 | 66.8 (8.0, 97.7) | 0.006 | (0.91, 1.18) | 0.05 | 2 | 2.192 | NA | NS |
| Melanoma | 4 | 2932 | 1.02 (0.97, 1.07) | 1.02 (0.97, 1.07) | 0.99 (0.92, 1.06) | 0.482 | 0 (0, 87.2) | 0.561 | (0.97, 1.07) | 0.722 | 0 | 0.597 | NA | NS |
| Ovarian cancer | 8 | 2985 | 0.97 (0.93, 1.01) | 0.96 (0.92, 1.01) | 1.00 (0.93, 1.07) | 0.129 | 20.8 (0, 88.3) | 0.265 | (0.89, 1.04) | 0.328 | 1 | 1.681 | NA | NS |
| Pancreatic cancer | 5 | 3837 | 1.01 (0.98, 1.03) | 0.98 (0.92, 1.04) | 1.04 (1.00, 1.08) | 0.537 | 63.7 (0, 99.4) | 0.026 | (0.87, 1.10) | 0.009 | 2 | 2.041 | NA | NS |
1
NS, not statistically significant, P > 0.05. NA, not available; P for Q, P value for heterogeneity, Cochran's Q test; PI, prediction interval.
2
The 95% CI for I2 cannot be calculated when the number of studies is <2.
3
From Egger's regression asymmetry test.
4
Observed number (O) and expected number (E) of significant studies (P < 0.05) using effect of largest study (smallest SE) of each meta-analysis as a plausible effect size.
5
Estimated expected number (E) is larger than observed number (O) and there is no evidence of excess significance. P value of excess significance test. All statistical tests are 2-sided.