TABLE 1.
Odds ratios and 95% confidence intervals for factors not modifiable after menopause in relation to postmenopausal invasive breast cancer risk, Wisconsin, Massachusetts, and New Hampshire, 1997–2001
| Factor | No. of controls | %* | No. of cases | %* | OR†‡ | 95% CI† | OR§ | 95% CI |
| First-degree family history of breast cancer | ||||||||
| No | 3,500 | 83.1 | 2,636 | 75.3 | 1 | Reference | 1 | Reference |
| Yes | 585 | 13.9 | 746 | 21.3 | 1.67 | 1.49, 1.89 | 1.66 | 1.46, 1.88 |
| Personal history of benign breast disease | ||||||||
| No | 3,318 | 78.8 | 2,432 | 69.5 | 1 | Reference | 1 | Reference |
| Yes | 832 | 19.8 | 986 | 28.2 | 1.64 | 1.48, 1.83 | 1.53 | 1.36, 1.71 |
| Height at age 25 years (m) | ||||||||
| <1.60 | 1,106 | 26.3 | 797 | 22.8 | 1 | Reference | 1 | Reference |
| 1.60–1.62 | 1,083 | 25.7 | 890 | 25.4 | 1.11 | 0.98, 1.26 | 1.11 | 0.98, 1.27 |
| 1.63–1.67 | 1,129 | 26.8 | 955 | 27.3 | 1.15 | 1.02, 1.31 | 1.14 | 1.00, 1.31 |
| ≥1.68 | 848 | 20.1 | 823 | 23.5 | 1.32 | 1.15, 1.50 | 1.27 | 1.09, 1.48 |
| Age at menarche (years) | ||||||||
| <12 | 863 | 20.5 | 770 | 22.0 | 1.36 | 1.15, 1.60 | 1.37 | 1.15, 1.63 |
| 12 | 924 | 21.9 | 822 | 23.5 | 1.35 | 1.14, 1.59 | 1.33 | 1.12, 1.58 |
| 13–14 | 1,820 | 43.2 | 1,480 | 42.3 | 1.22 | 1.05, 1.41 | 1.20 | 1.02, 1.40 |
| ≥15 | 531 | 12.6 | 355 | 10.2 | 1 | Reference | 1 | Reference |
| Age at menopause (years) | ||||||||
| <45 | 1,176 | 27.9 | 780 | 22.3 | 1 | Reference | 1 | Reference |
| 45–49 | 966 | 22.9 | 783 | 22.4 | 1.24 | 1.09, 1.41 | 1.22 | 1.06, 1.40 |
| 50–54 | 1,279 | 30.4 | 1,124 | 32.1 | 1.32 | 1.17, 1.50 | 1.25 | 1.09, 1.42 |
| ≥55 | 415 | 9.9 | 409 | 11.7 | 1.47 | 1.24, 1.73 | 1.40 | 1.18, 1.68 |
| Unknown | 377 | 9.0 | 403 | 11.5 | 1.58 | 1.34, 1.87 | 1.39 | 1.15, 1.67 |
| Age at first full-term pregnancy (years)¶ | ||||||||
| <20 | 827 | 21.8 | 597 | 19.5 | 1 | Reference | 1 | Reference |
| 20–24 | 2,010 | 53.0 | 1,568 | 51.3 | 1.10 | 0.97, 1.24 | 1.02 | 0.89, 1.16 |
| 25–29 | 740 | 19.5 | 654 | 21.4 | 1.28 | 1.10, 1.49 | 1.15 | 0.98, 1.36 |
| ≥30 | 202 | 5.3 | 236 | 7.7 | 1.69 | 1.36, 2.10 | 1.42 | 1.11, 1.80 |
| Parity | ||||||||
| 0–1 | 756 | 17.9 | 767 | 21.9 | 1.54 | 1.35, 1.76 | 1.35 | 1.12, 1.65 |
| 2 | 948 | 22.5 | 854 | 24.4 | 1.36 | 1.20, 1.54 | 1.26 | 1.10, 1.44 |
| 3 | 1,020 | 24.2 | 810 | 23.2 | 1.17 | 1.04, 1.32 | 1.13 | 0.99, 1.28 |
| ≥4 | 1,476 | 35.0 | 1,051 | 30.0 | 1 | Reference | 1 | Reference |
| Oral contraceptive use (months) | ||||||||
| 0 | 2,512 | 59.6 | 2,031 | 58.1 | 1 | Reference | 1 | Reference |
| 1–36 | 662 | 15.7 | 549 | 15.7 | 1.04 | 0.91, 1.19 | 1.04 | 0.91, 1.19 |
| >36 | 979 | 23.2 | 867 | 24.8 | 1.10 | 0.98, 1.23 | 1.09 | 0.97, 1.23 |
| Lactation duration (months)¶ | ||||||||
| 0 | 2,330 | 61.4 | 1,865 | 61.0 | 1 | Reference | 1 | Reference |
| 1–11 | 481 | 12.7 | 369 | 12.1 | 0.88 | 0.76, 1.02 | 0.90 | 0.77, 1.05 |
| 12–23 | 244 | 6.4 | 188 | 6.2 | 0.90 | 0.74, 1.10 | 0.86 | 0.70, 1.06 |
| ≥24 | 726 | 19.1 | 630 | 20.6 | 1.01 | 0.90, 1.14 | 1.05 | 0.92, 1.19 |
*
Because of missing data, some categories do not sum to 100%. N = 3,499 cases and 4,213 controls.
†
OR, odds ratio; CI, confidence interval.
‡
Adjusted for age and state of residence.
§
Adjusted for age, state of residence, weight at age 18 years, screening mammograms per year over the last 5 years, and all variables in tables 1 and 2.
¶
Parous women only.