TABLE 5.
Risk ratios (RRs) for recurrent adenoma by intervention group: stratified analyses of the Nurses' Health Study (NHS) and Health Professionals Follow-Up Study (HPFS) Folic Acid Prevention Trial1
| At least one adenoma |
||||
| Stratification variable | Placebo | Folic acid | Risk ratio (95% CI) | P value |
| no. cases/total n | no. cases/total n | |||
| Age | ||||
| ≤66 y | 42/130 | 33/133 | 0.79 (0.54, 1.17) | 0.24 |
| >66 y | 30/108 | 29/104 | 1.00 (0.64, 1.55) | 0.99 |
| Aspirin | ||||
| <2 tablets/wk | 38/139 | 33/134 | 0.88 (0.59, 1.32) | 0.54 |
| ≥2 tablets/wk | 34/99 | 29/103 | 0.85 (0.56, 1.30) | 0.46 |
| BMI | ||||
| ≤25 kg/m2 | 36/115 | 26/120 | 0.66 (0.43, 1.03) | 0.06 |
| >25 kg/m2 | 36/123 | 36/117 | 1.08 (0.73, 1.59) | 0.72 |
| Smoking status | ||||
| Never | 27/96 | 24/88 | 1.03 (0.64, 1.66) | 0.89 |
| Ever | 45/141 | 37/145 | 0.79 (0.54, 1.14) | 0.21 |
| Folate concentrations at baseline | ||||
| ≤7.5 ng/mL | 42/113 | 32/139 | 0.61 (0.42, 0.90) | 0.01 |
| >7.5 ng/mL | 30/124 | 30/98 | 1.28 (0.82, 1.99) | 0.27 |
| Alcohol intake | ||||
| ≤5.6 g/d | 31/117 | 33/122 | 1.00 (0.65, 1.53) | 1.00 |
| >5.6 g/d | 41/121 | 29/115 | 0.76 (0.51, 1.13) | 0.17 |
| Combination alcohol intake/folate baseline | ||||
| ≤5.6 g/d and gt7.5 ng/mL | 14/62 | 15/53 | 1.23 (0.64, 2.37) | 0.53 |
| >5.6 g/d and le7.5 ng/mL | 25/59 | 14/70 | 0.49 (0.28, 0.84) | 0.009 |
1
RRs were calculated by using a generalized linear model with a natural logarithm link function and Poisson distributed errors, which were adjusted for over- and underdispersion. Models included age at start of trial, sex, length of trial (3 compared with ≤6.5 y), and time between start of trial and last endoscopy (mo). All P values for interaction were >0.05, except for folate at baseline (P = 0.01) and combination alcohol/folate at baseline (P = 0.03).