Table 3.
Relative Risks (RRs) of adenoma by treatment assignment with combination folic acid, vitamin B, vitamin B12 (active) treatment vs placebo in the Women’s Antioxidant and Folic Acid Cardiovascular Study (WAFACS)*
| First follow-up endoscopy | All follow-up endoscopies (first–last) | |||||||
|---|---|---|---|---|---|---|---|---|
| Active (n=741) | Placebo (n=729) | RR (95% CI)† | RR (95% CI)‡ | Active (n=741) | Placebo (n=729) | RR (95% CI)§ | RR (95% CI)‖ | |
| Outcome | No. of individuals with adenomas/total participants | No. of individuals with adenomas/total participants | No. of individuals with adenomas/total participants | No. of individuals with adenomas/total participants | ||||
| At least one adenoma | 145/741 | 141/729 | 1.01 (0.82 to 1.24) | 0.97 (0.78 to 1.20) | 180/741 | 175/729 | 1.02 (0.85 to 1.23) | 1.00 (0.83 to 1.20) |
| Subsite of adenoma¶ | ||||||||
| ≥1 proximal adenoma§ | 68/740 | 79/727 | 0.84 (0.62 to 1.15) | 0.83 (0.61 to 1.14) | 101/739 | 110/726 | 0.91 (0.71 to 1.17) | 0.90 (0.70 to 1.17) |
| ≥1 distal adenoma | 66/740 | 54/727 | 1.20 (0.85 to 1.69) | 1.10 (0.77 to 1.57) | 79/739 | 71/726 | 1.10 (0.81 to 1.49) | 0.98 (0.71 to 1.34) |
| Size of adenoma¶ | ||||||||
| Small | 101/738 | 96/726 | 1.03 (0.80 to 1.34) | 1.00 (0.77 to 1.31) | 122/738 | 118/726 | 1.03 (0.82 to 1.30) | 1.02 (0.80 to 1.29) |
| Large | 41/738 | 42/726 | 0.96 (0.63 to 1.45) | 0.91 (0.59 to 1.40) | 55/738 | 54/726 | 1.01 (0.71 to 1.45) | 0.97 (0.67 to 1.40) |
| Stage of adenoma¶ | ||||||||
| Early | 74/724 | 71/708 | 1.02 (0.75 to 1.39) | 0.98 (0.71 to 1.34) | 89/722 | 88/703 | 0.99 (0.75 to 1.31) | 0.98 (0.74 to 1.30) |
| Advanced | 54/724 | 49/708 | 1.07 (0.74 to 1.56) | 1.03 (0.70 to 1.51) | 72/722 | 61/703 | 1.16 (0.83 to 1.60) | 1.06 (0.76 to 1.50) |
| No. of adenomas (first endoscopy only) | ||||||||
| 1 | 102/741 | 102/729 | 0.99 (0.76 to 1.27) | 0.97 (0.74 to 1.26) | NA | NA | NA | NA |
| ≥2 | 43/741 | 39/729 | 1.08 (0.71 to 1.64) | 0.93 (0.61 to 1.43) | NA | NA | NA | NA |
* The generalized linear model with a natural logarithm link function and Poisson distributed errors were used. CI = confidence interval; NA = not available; PMH = postmenopausal hormone.
† Basic models included the age at the start of trial (continuous) and the time between the start of trial and first endoscopy (months).
‡ Full models included the age at the start of trial (continuous), the time between start of trial and first endoscopy (months), body mass index (continuous), smoking status (current, past, or never), alcohol intake (continuous), physical activity (continuous), menopausal status and PMH use (premenopausal, uncertain, postmenopausal and current PMH use, postmenopausal and past PMH use, or postmenopausal and never use of PMH), baseline folate intake (continuous), baseline vitamin B6 intake (continuous), baseline vitamin B12 intake (continuous), history of cancer (yes or no), history of adenoma before random assignment (no adenoma, early adenoma, advanced adenoma, missing, or no endoscopy before random assignment), randomly assigned to receive vitamin E (yes or no), randomly assigned to receive vitamin C (yes or no), and randomly assigned to receive β-carotene (yes or no).
§ Basic models included age at start of trial (continuous) and time between start of the trial and last endoscopy (months).
‖ Full models are the same as those for all first follow-up endoscopies except that the time between the start of trial and last endoscopy (months) was used.
¶ The denominator does not include participants with missing or unknown information for site, size, or stage. It does include those with no adenoma for site, size, and stage.