Table 2.
Characteristics of premenopausal women in the study population: Group Health, Seattle, WA 2004 – 2005 (N = 175*)
| Age, y | ||
| Mean (SD) | 42.4 | (1.4) |
| Median (Range) | 43.0 | (40, 45) |
| Age at menarche, y | ||
| Mean (SD) | 12.8 | (1.3) |
| Median (Range) | 13.0 | (10, 17) |
| Age at first birth§, y | ||
| Mean (SD) | 28.8 | (5.9) |
| Median (Range) | 29.0 | (15, 40) |
| Body mass index, kg/m2 | ||
| Mean (SD) | 25.8 | (4.6) |
| Median (Range) | 25.0 | (19, 39) |
| Height, m | ||
| Mean (SD) | 1.65 | (0.07) |
| Median (Range) | 1.65 | (1.48, 1.84) |
| Weight, kg | ||
| Mean (SD) | 70.4 | (13.3) |
| Median (Range) | 68.0 | (46, 108) |
| Waist:Hip ratio | ||
| Mean (SD) | 0.79 | (0.06) |
| Median (Range) | 0.78 | (0.66, 1.00) |
| n | (%) | |
| Number of live births | ||
| 0 | 50 | (28.6) |
| 1 | 23 | (13.1) |
| 2+ | 83 | (47.4) |
| Had a history of breast-feeding§ | 100 | (81.3) |
| Had a history of hormone use† | 125 | (71.4) |
| First degree relative with breast and/or ovarian cancer | 22 | (12.6) |
| Smoking status | ||
| Current | 8 | (4.6) |
| Former | 54 | (30.9) |
| Never | 119 | (68.0) |
| Race / ethnicity | ||
| Asian | 13 | (7.4) |
| White | 152 | (86.9) |
| Other | 8 | (4.6) |
| Years of school completed | ||
| ≤ 12 | 12 | (6.9) |
| 13 – 15 | 48 | (27.4) |
| 16 | 49 | (28.0) |
| ≥ 17 years | 64 | (36.6) |
| Income | ||
| ≤ $49,999 | 28 | (16.0) |
| $50,000 – $75,000 | 41 | (23.4) |
| > $75,000 | 83 | (47.4) |
| No information provided | 21 | (12.0) |
*
Numbers (%) may not add up to 175 (100%) for some characteristics due to missing values and rounding calculations
§
Among parous women only (n = 123);
†
Use of oral contraceptives, hormone patches, hormone injections, hormone implants, or intrauterine devices containing progesterone at any time prior to the 6-month period before the screening mammogram