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Table 1 Baseline characteristics of breast cancer cases and controls with BRCA1 and BRCA2 mutations.

From: Breastfeeding and the risk of breast cancer in BRCA1 and BRCA2 mutation carriers

Characteristic BRCA1 BRCA2
  Controls
(n = 1,243)
Cases
(n = 1,243)
P Controls
(n = 422)
Cases
(n = 422)
P
Year of birth, mean (range) 1957.5 (1920-1980) 1957.3 (1920-1980) 0.71 1954.4 (1924-1978) 1955.3 (1924-1978) 0.82
Age at diagnosis, mean (range) n/a1 0.71 n/a1 n/a1 42.7 (24-67) n/a1
Country of residence, n (%)       
Poland 601 (48%) matched   0 (0%) matched  
USA 323 (26%)    187 (44%)   
Canada 265 (21%)    218 (52%)   
Israel 29 (2%)    13 (3%)   
Austria 18 (1.5%)    3 (0.7%)   
Italy 5 (0.4%)    0 (0%)   
United Kingdom 2 (0.2%)    2 (0.5%)   
Age at menarche, mean (range) 13.27(8-28) 13.09 (9-21) 0.003 12.64 (8-28) 12.15 (9-17) 0.88
Age at first birth, mean (range) 25.1 (15-44) 24.8 (15-42) 0.08 26.6 (17-44) 26.3 (16-42) 0.37
Age at last birth, mean (range) 29.3 (16-45) 29.0 (17-44) 0.06 30.5 (20-45) 30.2 (18-43) 0.96
Parity2,4, n (%)       
1 235 (19%)    65 (15%)   
2 663 (53%)    233 (55%)   
3 280 (23%)    100 (24%)   
≥ 4 65 (5%)    24 (6%)   
Mean (range) 2.16 (1-6) matched   2.20 (1-6) matched  
Breastfeeding, mean months3,4 (range) 10.4 (0-92) 8.8 (0-84) 0.0009 9.7 (0-94) 10.2 (0-86) 0.56
Oral contraceptive use4, ever, n (%) 644 (52%) 657 (53%) 0.95 348 (83.5%) 336 (80.2%) 0.22
Smoking status, ever, n (%) 549 (45%) 574 (46%) 0.74 185 (44.4%) 170 (40.9%) 0.31
Alcohol use, ever, n (%) 832 (67%) 760 (61%) 0.002 305 (73.3%) 284 (68.8%) 0.13
HRT use4, n (%) 148 (12%) 67 (5%) < 0.0001 69 (16.5%) 45 (10.7%) 0.02
BMI at age 30, mean (range) 22.5 (13-47) 22.6 (9-62) 0.24 22.8 (15-54) 23.0 (12-65) 0.48
  1. 1n/a, not applicable. 2Parity includes live births only. 3Breastfeeding is the total months of breastfeeding for each pregnancy combined. 4Parity, breastfeeding, oral contraceptive use and HRT use were censored one year prior to the diagnosis of the matched case for both cases and controls.