Table 1.
Summary risk estimates of the association between cruciferous vegetable consumption and colorectal cancer risk
| Number of studies | Summary RR (95% CI) | Q-statistic | I2 | Ph* | Ph** | |
|---|---|---|---|---|---|---|
| Value (%) | ||||||
| Overall studies | ||||||
| CV | 35 | 0.82 (0.75–0.90) | 98.57 | 66.5 | <0.001 | – |
| Cabbage | 9 | 0.76 (0.60–0.97) | 19.20 | 58.3 | 0.014 | – |
| Broccoli | 6 | 0.82 (0.65–1.02) | 11.07 | 54.8 | 0.050 | – |
| Subgroup analyses for CV | ||||||
| High-quality studies (scores ≥7) | 20 | 0.88 (0.80–0.97) | 48.57 | 60.9 | <0.001 | 0.046 |
| Study design | ||||||
| Prospective studies | 11 | 0.93 (0.87–1.00) | 15.40 | 35.1 | 0.118 | 0.025 |
| Case–control studies | 23 | 0.74 (0.65–0.84) | 74.37 | 70.4 | <0.001 | |
| Type of control subjects | ||||||
| Population based | 11 | 0.79 (0.66–0.93) | 35.18 | 71.6 | <0.001 | 0.487 |
| Hospital based | 9 | 0.71 (0.56–0.89) | 30.76 | 74.0 | <0.001 | |
| Geographic location | ||||||
| Europe | 10 | 0.89 (0.76–1.04) | 24.23 | 62.8 | 0.004 | 0.822 |
| America | 14 | 0.81 (0.72–0.92) | 34.51 | 62.3 | 0.001 | |
| Asia | 7 | 0.82 (0.64–1.05) | 16.86 | 64.4 | 0.010 | |
| Gender | ||||||
| Male | 16 | 0.80 (0.69–0.93) | 54.75 | 72.6 | <0.001 | 0.546 |
| Female | 16 | 0.87 (0.77–0.98) | 29.26 | 48.7 | 0.015 | |
| Anatomic cancer site | ||||||
| Colon | 16 | 0.78 (0.69–0.89) | 37.06 | 59.5 | 0.001 | 0.225 |
| Rectum | 9 | 0.91 (0.74–1.13) | 21.21 | 62.3 | 0.007 | |
| Cancer subsite of colon | ||||||
| Proximal | 6 | 0.80 (0.67–0.95) | 8.66 | 42.3 | 0.123 | 0.709 |
| Distal | 6 | 0.74 (0.56–0.98) | 13.84 | 63.9 | 0.017 | |
| Adjustment for confounders | ||||||
| Body mass index | ||||||
| Yes | 14 | 0.90 (0.85–0.95) | 16.58 | 21.6 | 0.219 | 0.020 |
| No | 19 | 0.70 (0.59–0.83) | 72.10 | 75.0 | <0.001 | |
| Alcohol | ||||||
| Yes | 15 | 0.89 (0.84–0.94) | 21.07 | 33.5 | 0.100 | 0.061 |
| No | 19 | 0.73 (0.61–0.86) | 73.77 | 75.6 | <0.001 | |
| Physical activity | ||||||
| Yes | 13 | 0.90 (0.85–0.96) | 15.62 | 23.2 | 0.209 | 0.060 |
| No | 21 | 0.72 (0.59–0.88) | 63.05 | 76.2 | <0.001 | |
| Total energy intake | ||||||
| Yes | 16 | 0.90 (0.85–0.95) | 16.14 | 7.0 | 0.373 | 0.014 |
| No | 18 | 0.71 (0.59–0.85) | 75.87 | 77.6 | <0.001 | |
| Meat intake | ||||||
| Yes | 9 | 0.92 (0.85–0.99) | 7.63 | 0 | 0.470 | 0.290 |
| No | 25 | 0.78 (0.69–0.89) | 86.33 | 72.2 | <0.001 | |
| Family history of CRC/adenomatous polyposis | ||||||
| Yes | 13 | 0.93 (0.87–0.99) | 15.76 | 23.9 | 0.202 | 0.020 |
| No | 21 | 0.73 (0.64–0.84) | 73.43 | 72.8 | <0.001 | |
| Smoking status | ||||||
| Yes | 14 | 0.91 (0.86–0.97) | 18.58 | 30.0 | 0.137 | 0.019 |
| No | 20 | 0.72 (0.62–0.84) | 72.68 | 73.9 | <0.001 | |
| Subgroup analyses for cabbage | ||||||
| High-quality studies (scores ≥7) | 2 | 0.88 (0.55–1.39) | 0 | 0 | 0.935 | 0.633 |
| Study design | ||||||
| Prospective studies | 1 | 0.96 (0.54–1.72) | N/A | N/A | N/A | 0.557 |
| Case–control studies | 8 | 0.74 (0.57–0.97) | 18.98 | 63.1 | 0.008 | |
| Subgroup analyses for broccoli | ||||||
| High-quality studies (scores ≥7) | 5 | 0.86 (0.76–0.97) | 10.55 | 43.1 | 0.103 | 0.576 |
| Study design | ||||||
| Prospective studies | 3 | 0.91 (0.80–1.03) | 1.41 | 0 | 0.494 | 0.359 |
| Case–control studies | 3 | 0.60 (0.32–1.13) | 7.32 | 72.7 | 0.026 | |
CI, confidence interval; CV, cruciferous vegetables; N/A, not available; RR, relative risk.
*P-value for heterogeneity within each subgroup.
**P-value for heterogeneity between subgroups with meta-regression analysis.