Table I.
Demographic characteristics of the study population
| Characteristic | Categories | Control (n = 494) | Case (n = 399) | P-value |
| Age (years) | Mean ± SD | 58.7 ± 11.8 | 57.4 ± 13.0 | 0.12 |
| ≤50 | 153 (31.0%) | 125 (31.3%) | 0.22 | |
| 51–60 | 109 (22.1%) | 110 (27.6%) | ||
| 61–70 | 136 (27.5%) | 95 (23.8%) | ||
| ≥71 | 96 (19.4%) | 69 (17.3%) | ||
| Race | African-American | 78 (15.8%) | 63 (15.8%) | 1.00 |
| Caucasian | 416 (84.2%) | 336 (84.2%) | ||
| FHa | No | 407 (82.4%) | 320 (80.2%) | 0.40 |
| Yes | 87 (17.6%) | 79 (19.8%) | ||
| Smoking historyb | No | 282 (57.4%) | 224 (57.6%) | 0.96 |
| Yes | 209 (42.6%) | 165 (42.4%) | ||
| Missing | 3 | 10 | ||
| Age at menarche | ≤12 | 219 (44.9%) | 173 (45.3%) | 0.27 |
| 13–14 | 215 (44.1%) | 154 (40.3%) | ||
| ≥15 | 54 (11.1%) | 55 (14.4%) | ||
| Missing | 6 | 17 | ||
| BMI | Mean ± SD | 27.20 ± 5.97 | 27.99 ± 6.37 | 0.06 |
| Missing | 3 | 10 | ||
| Age first live birth | ≤24 | 240 (49.1%) | 223 (57.6%) | 0.04 |
| 25–29 | 124 (25.4%) | 77 (19.9%) | ||
| ≥30 or nulliparous | 125 (25.6%) | 87 (22.5%) | ||
| Missing | 5 | 12 |
a
First-degree relatives with breast cancer (mother and/or sister).
b
Lifetime smoking history of at least 100 cigarettes.