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Table 1 Sample description

From: Reproductive risk factors in breast cancer and genetic hormonal pathways: a gene-environment interaction in the MCC-Spain project

Variable Category Cases (%) Controls (%) p
Age at recruitment < 45 years 214 (19) 234 (18) < 0.001
45–54 years 317 (28) 282 (21)  
55–64 years 296 (26) 290 (22)  
65–74 years 180 (16) 313 (24)  
≥ 75 years 132 (12) 203 (15)  
Educational level Unfinished primary 162 (14) 246 (19) 0.02
Primary studies 391 (34) 405 (31)  
Secondarystudies 366 (32) 405 (31)  
High education 220 (19) 266 (20)  
Parity Nulliparous 254 (22) 242 (18) 0.007
1 207 (18) 200 (15)  
2 445 (39) 516 (39)  
≥ 3 233 (21) 364 (28)  
Age at menarche ≤ 12 years 436 (38) 487 (37) 0.46
> 12 years 703 (62) 835 (63)  
Menopausal status Premenopausal 657 (59) 889 (67) < 0.001
Postmenopausal 464 (41) 433 (33)  
Age at menopause < 50 years 329 (47) 445 (50) 0.18
≥ 50 years 378 (53) 447 (50)  
Age at first delivery < 20 years 70 (8) 70 (7) 0.50
20–24 years 247 (28) 286 (28)  
25–29 years 329 (37) 410 (40)  
30–34 years 163 (19) 187 (18)  
≥ 35 years 69 (8) 64 (6)  
Tobacco use Non- smoker 607 (53) 792 (60) 0.001
Former smoker 304 (27) 274 (21)  
Current smoker 228 (20) 256 (19)  
Body Mass Index (kg/m2) < 18.5 15 (1) 26 (2) 0.34
18.5–24.9 527 (46) 638 (48)  
25.0–29.9 387 (34) 414 (31)  
≥ 30.0 210 (18) 244 (18)  
Family history of breast cancer No 764 (67) 1097 (83) < 0.001
First-degree relative 167 (14) 121 (9)  
Second-degree relative 24 (2) 14 (1)  
Other relative 178 (16) 89 (7)  
Hormonal contraceptive No 628 (55) 725 (55) 0.88
Yes 511 (45) 597 (45)  
Hormone replacement therapy No 1021 (90) 1177 (89) 0.70
Yes 83 (7) 100 (8)