Characteristics of treated and untreated participants [mean (SD) or proportions where applicable]
| Characteristics | Treated (n = 167) | Untreated (n = 142) | P |
|---|---|---|---|
| Age (y), mean (SD) | |||
| At interview | 48.4 (4.8) | 46.2 (4.1) | <0.001 |
| At mammogram | 48.0 (4.7) | 45.8 (4.1) | <0.001 |
| Postmenopausal* (%) | 57 (34.1) | 25 (17.6) | 0.001 |
| Age at menarche (y),† mean (SD) | 12.8 (1.6) | 12.8 (1.4) | 0.86 |
| Live births (%) | |||
| 0 | 36 (21.6) | 26 (18.3) | 0.48‡ |
| 1 | 23 (13.8) | 11 (7.8) | |
| ≥2 | 108 (64.7) | 105 (74) | |
| Age at first live birth (y), mean (SD) | 30.0 (4.6) | 29.4 (4.5) | 0.25 |
| Height (cm), mean (SD) | 178.4 (3.8) | 175.6 (4.7) | <0.001 |
| Weight (kg), mean (SD) | 78.4 (16.2) | 79.9 (15.7) | 0.40 |
| BMI (kg/m2), mean (SD) | 24.6 (5.2) | 25.9 (4.9) | 0.030 |
| Birthweight (kg),§ mean (SD) | 3.6 (0.51) | 3.5 (0.49) | 0.13 |
| Birth length (cm),∥ mean (SD) | 53.2 (2.5) | 52.9 (2.4) | 0.53 |
| EMH-final height (cm),¶ mean (SD) | 2.1 (2.8) | −1.0 (3.2) | <0.001 |
| Fertility drugs (ever used; %) | 43 (25.8) | 18 (12.7) | 0.004 |
| HRT | |||
| Ever used (%) | 35 (21.0) | 15 (10.6) | 0.013 |
| Current use (%) | 22 (13.2) | 7 (4.9) | 0.013 |
| Total use (y), mean (SD) | 3.9 (6.2) | 2.6 (3.1) | 0.073 |
| Hormonal contraceptive | |||
| Ever used (%) | 161 (96.4) | 138 (97.2) | 0.70 |
| Current use (%) | 20 (12.0) | 22 (15.5) | 0.37 |
| Total use (y), mean (SD) | 10.1 (7.2) | 11.9 (6.7) | 0.028 |
| Family history of breast cancer: first-degree relative (%) | 27 (16.2) | 19 (13.4) | 0.49 |
| Smoking (%) | |||
| Ever smoked | 88 (52.7) | 83 (58.4) | 0.31 |
| Currently smoke | 18 (10.8) | 17 (12.0) | 0.74 |
| Alcohol use (%) | |||
| Never or rarely drink | 24 (14.3) | 24 (16.9) | 0.24 |
| Occasionally (less than once a week) | 28 (16.8) | 25 (17.6) | |
| Once or twice a week | 33 (19.8) | 34 (23.9) | |
| ≥3 d/wk | 82 (49.1) | 59 (41.5) | |
| Benign breast disease (%) | 37 (22.2) | 23 (16.2) | 0.19 |
| Endometriosis** (%) | 30 (18.0) | 16 (11.3) | 0.10 |
| Total breast area (cm2) | |||
| Median (5th and 95th percentile range) | 102.6 (49.7-232.9) | 111.8 (57.4-236.0) | |
| Mean (SD) | 114.5 (57.2) | 123.9 (55.5) | 0.15 |
| Dense area (cm2) | |||
| Median (5th and 95th percentile range) | 26.4 (3.1-60.0) | 27.8 (4.7-77.6) | |
| Mean (SD) | 27.6 (17.6) | 32.8 (22.8) | 0.022 |
| Nondense area (cm2) | |||
| Median (5th and 95th percentile range) | 71.7 (18.5-226.9) | 69.2 (27.0-225.8) | |
| Mean (SD) | 87.0 (60.5) | 91.1 (59.8) | 0.55 |
| Percent density (%) | |||
| Median (5th and 95th percentile range) | 26.8 (2.2-67.1) | 28.2 (2.5-66.1) | |
| Mean (SD) | 29.5 (20.4) | 30.8 (19.6) | 0.58 |
↵*Women were defined as postmenopausal if the time since their last period was ≥52 weeks and (a) they had not started HRT before their periods ended or (b) they started HRT before their periods ended and they were ages ≥55 years.
↵†Age at menarche: 1 missing.
↵‡P value for ever live birth.
↵§Birthweight: n = 72 treated and 112 untreated.
↵∥Birth length: n = 48 treated and 58 untreated.
↵¶EMH: n = 251.
↵**Endometriosis: 2 missing.