Table 1.
Distribution of demographic characteristics and known breast cancer risk factors for case patients and control subjects included in the study*
| Category | Case patients (n = 5792) | Control subjects (n = 5830) |
|---|---|---|
| Source of study subjects, No. | ||
| SBCS | 2638 | 2707 |
| SWHS | 138 | 2261 |
| SBCSS/SECS | 3016 | 862 |
| Demographic factors | ||
| Age, y | 52.3±9.8 | 52.9±9.3 |
| Education ≥ middle school, % | 63.4 | 53.5 |
| Reproductive risk factors | ||
| Age at menarche, y | 14.4±1.7 | 14.8±1.8 |
| Postmenopausal, % | 46.9 | 49.6 |
| Age at menopause, y† | 49.1±4.4 | 48.5±4.3 |
| Age at first live birth, y‡ | 26.8±4.3 | 26.2±3.9 |
| Other risk factors | ||
| First-degree relative with breast cancer, % | 5.0 | 2.4 |
| Body mass index, kg/m2 | 23.95±3.45 | 23.69±3.38 |
| Waist-to-hip ratio | 0.83±0.06 | 0.81±0.06 |
* Unless otherwise specified, data are mean ± standard deviation. SBCS = Shanghai Breast Cancer Study; SBCSS/SECS = Shanghai Breast Cancer Survival Study/Shanghai Endometrial Cancer Study; SWHS = Shanghai Women’s Health Study.
† Among postmenopausal women.
‡ Among parous women.