Table 3.
Soy intake and risk of incident breast cancer according to menopausal status
| No. of cases | Person-years | Incidence rate (per 100,000 person-years)a | Adjusted hazard ratio (95% confidence intervals)b | |
|---|---|---|---|---|
| Baseline frequency (P for interaction = 0.856) | ||||
| Pre-menopause | ||||
| Monthly or lessc | 376 | 629,714 | 73.6 | 1.00 |
| 1–3 days/week | 628 | 709,199 | 78.9 | 0.99 (0.85–1.15) |
| ≥ 4 days/week | 116 | 127,684 | 76.8 | 0.90 (0.71–1.13) |
| P for trendd | 0.433 | |||
| Post-menopause | ||||
| Monthly or lessc | 364 | 634,634 | 72.4 | 1.00 |
| 1–3 days/week | 663 | 762,614 | 76.3 | 0.94 (0.81–1.09) |
| ≥ 4 days/week | 142 | 151,706 | 79.3 | 0.93 (0.75–1.15) |
| P for trendd | 0.446 | |||
| Quartiles of usual soy isoflavone intake (P for interaction = 0.972) | ||||
| Pre-menopause | ||||
| Q1 | 233 | 452,731 | 66.4 | 1.00 |
| Q2 | 157 | 229,605 | 73.5 | 1.00 (0.79–1.28) |
| Q3 | 652 | 706,875 | 81.8 | 1.11 (0.91–1.35) |
| Q4 | 78 | 77,386 | 80.6 | 1.00 (0.74–1.35) |
| P for trende | 0.556 | |||
| Post-menopause | ||||
| Q1 | 262 | 541,110 | 68.9 | 1.00 |
| Q2 | 154 | 287,411 | 70.4 | 0.89 (0.70–1.13) |
| Q3 | 657 | 637,395 | 79.0 | 0.99 (0.81–1.21) |
| Q4 | 96 | 83,039 | 79.3 | 0.97 (0.73–1.28) |
| P for trende | 0.872 | |||
aValues were adjusted for study region and age at study date
bAdjusted for the same variables as model 3 in Table 2, except menopausal status
cThe “Never or rarely” and “Monthly” groups were combined into the “Monthly or less” to ensure enough cases in each frequency category
dTest for trend was conducted by coding the “Monthly or less” group as 1, “1-3 days/week” group as 2, and “≥4 days/week” group as 3
eTest for trend was conducted by coding from the lowest to the highest quartile into 1, 2, 3 and 4, respectively