Sensitivity analyses on study level of population, intervention and time to outcome assessment
| Sensitivity analysis on study level | RR (95% CI) |
| All | 1.07 (1.00 to 1.14) |
| <70% men11 22 23 25 26 | 1.05 (0.90 to 1.23) |
| >70% men12 24 27 28 | 1.08 (1.00 to 1.16) |
| <30% smokers11 23–28 | 1.05 (0.98 to 1.12) |
| >30% smokers12 | 1.19 (1.02 to 1.38) |
| <15% smokers23 26–28 | 1.04 (0.97 to 1.13) |
| >15% smokers11 12 24 25 | 1.12 (0.93 to 1.35) |
| History of colorectal adenoma11 22 23 | 1.28 (0.95 to 1.72) |
| History of cardiovascular disease12 24–28 | 1.06 (0.99 to 1.13) |
| 0.4–1 mg folic acid/day11 12 22 23 | 1.21 (1.06 to 1.38) |
| >1 mg folic acid/day24–28 | 1.03 (0.96 to 1.11) |
| <5 years exposure12 22 24 25 | 1.10 (0.97 to 1.23) |
| >5 years exposure11 23 26–28 | 1.06 (0.97 to 1.17) |
| <5 years follow-up22 24 25 | 0.95 (0.78 to 1.17) |
| >5 years follow-up11 12 23 26–28 | 1.09 (1.00 to 1.18) |
| Folic acid given in combination with other B vitamins12 24–28 | 1.06 (0.99 to 1.13) |
| Folic acid given with aspirin11 22 | 1.43 (1.00 to 2.03) |
| Folic acid given in countries with fortification24 26 | 0.95 (0.81 to 1.13) |