Table 2.
Relative risk (RR) and 95% confidence intervals (95%CI) for breast cancer according to quintile of energy-adjusted carbohydrate quality and quantity, insulin index and insulin load in 1991 among women in the Nurses’ Health Study II
| Quintile of intake | ||||||
|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | Ptrend | |
| Carbohydrate | ||||||
| All cases | ||||||
| Median intake, percent of energy | 40.6 | 45.9 | 49.6 | 53.3 | 59.2 | |
| No. of cases/person-years | 620/351,424 | 576/351,534 | 573/351,468 | 572/351,442 | 549/351,375 | |
| Age-adjusted RR (95%CI) | 1 | 0.94 (0.84–1.06) | 0.96 (0.86–1.08) | 0.95 (0.85–1.07) | 0.93 (0.83–1.04) | 0.25 |
| Multivariable RR (95%CI) | 1 | 0.93 (0.83–1.04) | 0.93 (0.83–1.04) | 0.92 (0.82–1.03) | 0.89 (0.79–1.00) | 0.07 |
| Premenopausal cases | ||||||
| Median intake, percent of energy | 40.6 | 45.9 | 49.6 | 53.3 | 59.2 | |
| No. of cases/person-years | 333/218,609 | 320/218,603 | 286/218,414 | 322/218,369 | 286/218,225 | |
| Age-adjusted RR (95%CI) | 1 | 0.97 (0.83–1.13) | 0.88 (0.75–1.03) | 1.00 (0.86–1.17) | 0.90 (0.77–1.06) | 0.30 |
| Multivariable RR (95%CI) | 1 | 0.96 (0.82–1.12) | 0.86 (0.74–1.02) | 0.98 (0.84–1.15) | 0.87 (0.74–1.03) | 0.15 |
| Postmenopausal cases | ||||||
| Median intake, percent of energy | 40.0 | 45.5 | 49.2 | 53.0 | 59.0 | |
| No. of cases/person-years | 199/85,958 | 154/86,001 | 197/86,102 | 180/86,235 | 189/86,091 | |
| Age-adjusted RR (95%CI) | 1 | 0.76 (0.62–0.94) | 1.00 (0.82–1.22) | 0.90 (0.74–1.11) | 0.93 (0.76–1.14) | 0.94 |
| Multivariable RR (95%CI) | 1 | 0.74 (0.60–0.92) | 0.96 (0.78–1.18) | 0.86 (0.70–1.06) | 0.88 (0.72–1.09) | 0.56 |
| Glycemic index | ||||||
| All cases | ||||||
| Median | 49.7 | 52.3 | 54.0 | 55.6 | 57.9 | |
| No. of cases/person-years | 599/351,303 | 591/351,648 | 603/351,157 | 559/351,454 | 538/351,682 | |
| Age-adjusted RR (95%CI) | 1 | 1.01 (0.90–1.13) | 1.05 (0.94–1.18) | 0.99 (0.88–1.11) | 0.98 (0.87–1.10) | 0.69 |
| Multivariable RR (95%CI) | 1 | 1.00 (0.90–1.13) | 1.06 (0.95–1.19) | 1.01 (0.90–1.14) | 1.01 (0.90–1.14) | 0.80 |
| Premenopausal cases | ||||||
| Median | 49.7 | 52.3 | 54.0 | 55.6 | 57.9 | |
| No. of cases/person-years | 329/218,428 | 307/218,399 | 308/218,432 | 308/218,474 | 295/218,486 | |
| Age-adjusted RR (95%CI) | 1 | 0.97 (0.83–1.13) | 0.99 (0.85–1.16) | 1.02 (0.87–1.19) | 1.01 (0.86–1.18) | 0.77 |
| Multivariable RR (95%CI) | 1 | 0.98 (0.84–1.15) | 1.02 (0.88–1.20) | 1.05 (0.90–1.24) | 1.06 (0.90–1.25) | 0.32 |
| Postmenopausal cases | ||||||
| Median | 49.4 | 52.1 | 53.8 | 55.5 | 57.8 | |
| No. of cases/person-years | 174/86,049 | 196/86,096 | 204/86,113 | 166/86,048 | 179/86,082 | |
| Age-adjusted RR (95%CI) | 1 | 1.14 (0.93–1.40) | 1.21 (0.98–1.48) | 0.99 (0.80–1.23) | 1.08 (0.87–1.33) | 0.84 |
| Multivariable RR (95%CI) | 1 | 1.13 (0.92–1.39) | 1.20 (0.97–1.47) | 0.99 (0.79–1.23) | 1.07 (0.86–1.33) | 0.87 |
| Glycemic load | ||||||
| All cases | ||||||
| Median | 95.6 | 110.1 | 120.1 | 130.9 | 148.6 | |
| No. of cases/person-years | 622/351,436 | 580/351,501 | 563/351,440 | 556/351,550 | 569/351,317 | |
| Age-adjusted RR (95%CI) | 1 | 0.96 (0.85–1.07) | 0.94 (0.84–1.06) | 0.94 (0.84–1.06) | 0.97 (0.86–1.09) | 0.58 |
| Multivariable RR (95%CI) | 1 | 0.94 (0.84–1.05) | 0.92 (0.82–1.03) | 0.91 (0.81–1.02) | 0.95 (0.84–1.07) | 0.34 |
| Premenopausal cases | ||||||
| Median | 95.6 | 110.0 | 120.0 | 130.9 | 148.6 | |
| No. of cases/person-years | 351/218,590 | 303/218,532 | 293/218,479 | 297/218,296 | 303/218,321 | |
| Age-adjusted RR (95%CI) | 1 | 0.88 (0.76–1.03) | 0.88 (0.75–1.02) | 0.90 (0.77–1.05) | 0.93 (0.80–1.09) | 0.48 |
| Multivariable RR (95%CI) | 1 | 0.89 (0.76–1.04) | 0.87 (0.74–1.02) | 0.89 (0.76–1.04) | 0.92 (0.79–1.09) | 0.41 |
| Postmenopausal cases | ||||||
| Median | 94.1 | 108.8 | 119.0 | 129.9 | 147.8 | |
| No. of cases/person-years | 191/85,946 | 174/86,070 | 176/86,115 | 184/86,148 | 194/86,109 | |
| Age-adjusted RR (95%CI) | 1 | 0.91 (0.74–1.12) | 0.94 (0.76–1.15) | 0.98 (0.80–1.20) | 1.02 (0.83–1.24) | 0.67 |
| Multivariable RR (95%CI) | 1 | 0.90 (0.72–1.10) | 0.91 (0.74–1.12) | 0.94 (0.76–1.16) | 0.97 (0.79–1.20) | 1.00 |
| Dietary insulin index | ||||||
| All cases | ||||||
| Median | 38.0 | 41.1 | 43.1 | 45.2 | 48.4 | |
| No. of cases/person-years | 649/351,064 | 542/351,806 | 602/351,431 | 558/351,310 | 539/351,633 | |
| Age-adjusted RR (95%CI) | 1 | 0.86 (0.77–0.97) | 0.98 (0.88–1.10) | 0.93 (0.83–1.04) | 0.89 (0.80–1.00) | 0.17 |
| Multivariable RR (95%CI) | 1 | 0.87 (0.77–0.98) | 0.99 (0.88–1.11) | 0.93 (0.83–1.05) | 0.90 (0.80–1.02) | 0.24 |
| Premenopausal cases | ||||||
| Median | 38.0 | 41.1 | 43.1 | 45.2 | 48.4 | |
| No. of cases/person-years | 356/218,269 | 283/218,764 | 333/218,300 | 285/218,467 | 290/218,420 | |
| Age-adjusted RR (95%CI) | 1 | 0.82 (0.71–0.97) | 1.00 (0.86–1.16) | 0.87 (0.74–1.02) | 0.89 (0.76–1.04) | 0.24 |
| Multivariable RR (95%CI) | 1 | 0.85 (0.72–1.00) | 1.04 (0.88–1.21) | 0.92 (0.78–1.08) | 0.93 (0.79–1.10) | 0.64 |
| Postmenopausal cases | ||||||
| Median | 37.6 | 40.8 | 42.8 | 44.9 | 48.2 | |
| No. of cases/person-years | 193/85,826 | 175/86,013 | 194/86,255 | 190/86,103 | 167/86,190 | |
| Age-adjusted RR (95%CI) | 1 | 0.93 (0.75–1.14) | 1.02 (0.83–1.24) | 1.01 (0.83–1.24) | 0.88 (0.71–1.08) | 0.40 |
| Multivariable RR (95%CI) | 1 | 0.92 (0.75–1.14) | 1.02 (0.82–1.25) | 0.99 (0.80–1.22) | 0.86 (0.69–1.07) | 0.29 |
| Insulin load | ||||||
| All cases | ||||||
| Median | 682 | 739 | 777 | 817 | 882 | |
| No. of cases/person-years | 635/352,963 | 564/352,499 | 580/347,330 | 564/352,174 | 547/352,278 | |
| Age-adjusted RR (95%CI) | 1 | 0.92 (0.82–1.02) | 0.97 (0.87–1.09) | 0.96 (0.85–1.07) | 0.93 (0.82–1.04) | 0.33 |
| Multivariable RR (95%CI) | 1 | 0.92 (0.82–1.03) | 0.98 (0.87–1.10) | 0.96 (0.85–1.08) | 0.92 (0.82–1.04) | 0.35 |
| Premenopausal cases | ||||||
| Median | 682 | 739 | 777 | 817 | 882 | |
| No. of cases/person-years | 344/218,377 | 298/218,488 | 327/217,827 | 283/219,793 | 295/217,735 | |
| Age-adjusted RR (95%CI) | 1 | 0.89 (0.76–1.04) | 1.00 (0.86–1.17) | 0.89 (0.76–1.04) | 0.93 (0.79–1.09) | 0.38 |
| Multivariable RR (95%CI) | 1 | 0.91 (0.78–1.07) | 1.04 (0.89–1.22) | 0.93 (0.79–1.09) | 0.97 (0.82–1.14) | 0.77 |
| Postmenopausal cases | ||||||
| Median | 674 | 732 | 771 | 812 | 878 | |
| No. of cases/person-years | 190/85,674 | 176/86,147 | 192/86,364 | 187/86,144 | 174/86,059 | |
| Age-adjusted RR (95%CI) | 1 | 0.94 (0.77–1.16) | 1.02 (0.83–1.24) | 1.01 (0.82–1.23) | 0.92 (0.75–1.13) | 0.61 |
| Multivariable RR (95%CI) | 1 | 0.94 (0.76–1.16) | 1.01 (0.82–1.24) | 0.99 (0.80–1.22) | 0.90 (0.72–1.12) | 0.45 |
Ptrend calculated with median intake of each variable in each quintile as a continuous variable.
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 race (white, non-white), family history of breast cancer in mother or sisters (yes, no), history of benign breast disease (yes, no), smoking (never, past, current 1 to 14/day, current 15 to 24/day, current ≥25/day), height (<62, 62 to <65, 65 to <68, ≥68 inches), BMI at age 18 years (<18.5, 18.5 to <20.0, 20.0 to <22.5, 22.5 to <25.0, 25.0 to <30.0, ≥30.0 kg/m2), weight gain since age 18 (≤−5, >−5–5, >5–10, >10–20, >20 kg), age at menarche (<12, 12, 13, ≥14 years), parity and age at first birth (nulliparous, parity ≤2 and age at first birth <25 years, parity≤2 and age at first birth 25 to <30 years, parity ≤2 and age at first birth ≥30 years, parity 3 to 4 and age at first birth <25 years, parity 3 to 4 and age at first birth 25 to <30 years, parity 3 to 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), oral contraceptive use (never, past, current), alcohol intake (nondrinker, <5, 5 to <15, ≥15 g/day), and energy (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).