Table 1.

Baseline characteristics of breast cancer cases and controls with BRCA1 and BRCA2 mutations

CharacteristicControls (n = 2,854)Cases (n = 2,854)P
Date of birth, mean (range)1957.1 (1911–1982)1957.0 (1911–1983)0.71
Age at interview, mean (range), y47.1 (21–85)46.8 (18–86)0.19
Age at diagnosis, mean (range), yn/a40.4 (19–76)
Mutation, n (%)
 BRCA12,055 (72.0)
 BRCA2799 (28.0)Matched
Country of residence, n (%)
United States992 (34.8)
Canada804 (28.2)
Israel99 (3.5)
Poland724 (25.4)
Other countries235 (8.2)Matched
Parity, n (%)
Parous2,241 (78.5)2,286 (80.1)
Nulliparous613 (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 (%)
No2,361 (82.7)2,446 (85.7)0.002
Yes493 (17.3)408 (14.3)
Age at menopause, mean (range), y44.2 (12–58)45.3 (24–59)0.01
Age at natural menopause, mean (range), y47.90 (33–58)48.05 (33–59)0.71
Age at surgical menopause, mean (range),a y40.2 (12–55)41.0 (25–54)0.27
Oral contraceptive use, n (%)
Never1,042 (36.7)1,002 (35.4)
Ever1,796 (63.3)1,832 (64.6)0.29
Years used, mean (SD)3.91 (0–29)4.14 (0.28)0.11
Cumulative ovulatory cycles, mean (range)b242.9 (0–578)248.0 (0–532)0.07

Abbreviation: n/a, not applicable.

  • aAmong women who had surgical menopause (n = 123 cases and n = 213 controls).

  • bEstimated among subjects who had no information missing for the components needed to calculate cumulative ovulatory cycles (n = 2,518 cases and n = 2,567 controls).