Table 2.
Relative risks (RR) and 95% confidence intervals (95%CI) for breast cancer according to quintile of cumulative average of premenopausal whole grain and refined grain foods intake among women in the Nurses’ Health Study II
| Quintile of intake | ||||||
|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | Ptrend | |
| Cumulative average of premenopausal total whole grain-food intake | ||||||
| All cases | ||||||
| Median intake, serving/day | 0.2 | 0.5 | 0.7 | 1.0 | 1.5 | |
| No. of cases/person-years | 673/375,194 | 642/377,729 | 617/377,311 | 647/377,992 | 656/377,630 | |
| Age-adjusted RR (95%CI) | 1 | 0.99 (0.89–1.10) | 0.95 (0.85–1.06) | 1.01 (0.90–1.12) | 1.01 (0.90–1.12) | 0.76 |
| Multivariable RR (95%CI)† | 1 | 0.92 (0.83–1.03) | 0.87 (0.77–0.97) | 0.91 (0.81–1.02) | 0.91 (0.81–1.03) | 0.25 |
| Premenopausal cases | ||||||
| Median intake, serving/day | 0.2 | 0.5 | 0.7 | 1.00 | 1.5 | |
| No. of cases/person-years | 386/234,866 | 339/236,307 | 343/236,657 | 322/236,936 | 329/236,277 | |
| Age-adjusted RR (95%CI) | 1 | 0.89 (0.77–1.03) | 0.90 (0.77–1.04) | 0.85 (0.74–0.99) | 0.86 (0.74–1.00) | 0.06 |
| Multivariable RR (95%CI)† | 1 | 0.88 (0.76–1.02) | 0.87 (0.75–1.02) | 0.83 (0.71–0.97) | 0.82 (0.70–0.97) | 0.03 |
| Postmenopausal cases | ||||||
| Median intake, serving/day | 0.2 | 0.5 | 0.7 | 1.0 | 1.6 | |
| No. of cases/person-years | 223/105,700 | 243/106,194 | 216/106,298 | 233/106,309 | 254/106,231 | |
| Age-adjusted RR (95%CI) | 1 | 1.11 (0.92–1.33) | 0.99 (0.82–1.20) | 1.07 (0.89–1.29) | 1.14 (0.95–1.37) | 0.21 |
| Multivariable RR (95%CI)† | 1 | 1.05 (0.87–1.26) | 0.91 (0.75–1.11) | 0.99 (0.81–1.21) | 1.06 (0.87–1.30) | 0.61 |
| Cumulative average of premenopausal total refined grain-food intake | ||||||
| All cases | ||||||
| Median intake, serving/day | 1.2 | 1.7 | 2.2 | 2.7 | 3.5 | |
| No. of cases/person-years | 684/376,472 | 677/377,439 | 642/377,614 | 638/377,317 | 594/377,014 | |
| Age-adjusted RR (95%CI) | 1 | 1.03 (0.92–1.14) | 0.99 (0.89–1.10) | 1.00 (0.89–1.11) | 0.93 (0.83–1.03) | 0.12 |
| Multivariable RR (95%CI)† | 1 | 0.97 (0.86–1.08) | 0.92 (0.81–1.03) | 0.93 (0.81–1.05) | 0.88 (0.76–1.01) | 0.06 |
| Premenopausal cases | ||||||
| Median intake, serving/day | 1.3 | 1.8 | 2.2 | 2.7 | 3.5 | |
| No. of cases/person-years | 365/235,558 | 370/236,446 | 337/236,531 | 338/236,476 | 309/236,032 | |
| Age-adjusted RR (95%CI) | 1 | 1.03 (0.89–1.20) | 0.98 (0.84–1.13) | 0.99 (0.86–1.15) | 0.92 (0.79–1.07) | 0.20 |
| Multivariable RR (95%CI)† | 1 | 1.03 (0.88–1.20) | 0.97 (0.83–1.15) | 0.99 (0.83–1.18) | 0.91 (0.75–1.11) | 0.31 |
| Postmenopausal cases | ||||||
| Median intake, serving/day | 1.2 | 1.7 | 2.1 | 2.6 | 3.4 | |
| No. of cases/person-years | 250/105,946 | 239/106,239 | 230/106,239 | 221/106,186 | 229/106,069 | |
| Age-adjusted RR (95%CI) | 1 | 0.97 (0.82–1.16) | 0.94 (0.79–1.13) | 0.92 (0.76–1.10) | 0.93 (0.77–1.11) | 0.34 |
| Multivariable RR (95%CI)† | 1 | 0.92 (0.76–1.11) | 0.84 (0.69–1.03) | 0.81 (0.65–1.00) | 0.83 (0.66–1.04) | 0.10 |
Multivariable model was stratified by age in months at start of follow-up and calendar year of the current questionnaire cycle and was simultaneously adjusted for smoking (never, past, current 1–14/day, current 15–24/day, current ≥25/day), race (white/non-white), parity and age at first birth (nulliparous, parity ≤2 and age at first birth <25 years, parity≤2 and age at first birth 25–<30 years, parity ≤2 and age at first birth ≥30 years, parity 3–4 and age at first birth <25 years, parity 3–4 and age at first birth 25–<30 years, parity 3–4 and age at first birth ≥30 years, parity ≥5 and age at first birth <25 years, parity ≥5 and age at first birth ≥25 years), height (<62, 62–<65, 65–<68, ≥68 inches), BMI at age 18 years (<18.5, 18.5–<22.5, 22.5–<25, 25.0–<30, ≥30.0 kg/m2), weight change since age 18 (continuous, missing indicator), age at menarche (<12, 12, 13, ≥14 years), family history of breast cancer (yes, no), history of benign breast disease (yes, no), oral contraceptive use (never, past, current), adult alcohol intake (nondrinker, <5, 5–<15,≥15 g/day), physical activity (quintile), energy intake (quintile). In postmenopausal women, we additionally adjusted for hormone use (postmenopausal never users, postmenopausal past users, postmenopausal current users), age at menopause (<45 years, 45 to 46 years, 47 to 48, 49 to 50 years, 51 to 52 years, ≥53 years). Among all women, we additionally adjusted for hormone use and menopausal status (premenopausal, postmenopausal never users, postmenopausal past users, postmenopausal current users, unknown menopausal status) and, age at menopause (premenopausal, unknown menopause, <45 years, 45 to 46 years, 47 to 48, 49 to 50 years, 51 to 52 years, ≥53 years).