Table 1.
Baseline characteristics of breast cancer cases and controls with BRCA1 and BRCA2 mutations.
| Characteristic | Controls (n = 2,854) | Cases (n = 2,854) | P |
|---|---|---|---|
| Date of birth, mean (range) | 1957.1 (1911–82) | 1957.0 (1911–83) | 0.71 |
| Age at interview, mean (range | 47.1 (21–85) | 46.8 (18–86) | 0.19 |
| Age at diagnosis, mean (range) | n/a1 | 40.4 (19–76) | |
| Mutation, n (%) | |||
| BRCA1 | 2055 (72.0%) | ||
| BRCA2 | 799 (28.0%) | matched | |
| Country of residence, n (%) | |||
| United States | 992 (34.8%) | ||
| Canada | 804 (28.2%) | ||
| Israel | 99 (3.5%) | ||
| Poland | 724 (25.4%) | ||
| Other Countries | 235 (8.2%) | matched | |
| Parity, n (%) | |||
| Parous | 2241(78.5%) | 2286 (80.1%) | |
| Nulliparous | 613 (21.5%) | 568 (19.9%) | 0.14 |
| Mean (range) | 1.81(0–8) | 1.77 (0–8) | 0.30 |
| Months breastfed, mean (range) | 9.6 (0–147) | 7.5 (0–102) | <0.0001 |
| Age at menarche, mean (range) | 13.03(8–27) | 12.91(8–30) | 0.005 |
| Menopausal, n (%) | |||
| No | 2361 (82.7%) | 2446 (85.7%) | 0.002 |
| Yes | 493 (17.3%) | 408 (14.3%) | |
| Age at menopause, mean (range) | 44.2 (12–58) | 45.3(24–59) | 0.01 |
| Age at natural menopause, mean (range) | 47.90 (33–58) | 48.05 (33–59) | 0.71 |
| Age at surgical menopause, mean (range)2 | 40.2 (12–55) | 41.0 (25–54) | 0.27 |
| Oral contraceptive use, n (%) | |||
| Never | 1042 (36.7%) | 1002 (35.4%) | |
| Ever | 1796 (63.3%) | 1832 (64.6%) | 0.29 |
| Years used, mean (SD) | 3.91 (0–29) | 4.14 (0.28) | 0.11 |
| Cumulative ovulatory cycles, mean (range)3 | 242.9 (0–578) | 248.0 (0–532) | 0.07 |
1
n/a = not applicable.
2
Among women who had surgical menopause (n = 123 cases and n = 213 controls).
3
Estimated among subjects that had no information missing for the components needed to calculate cumulative ovulatory cycles (n = 2,518 cases and n = 2,567 controls).
only among women who had information available for all the necessary variables (see Methods for individual components used to estimate ovulatory cycles).