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Table 2 Distribution of demographic characteristics and known breast cancer risk factors for cases and controls included in the study

From: Breast cancer risk assessment with five independent genetic variants and two risk factors in Chinese women

Variables Testing Set, TS (n= 1,778) Validation Set, VS (n= 1,881) TS + VS (n= 3,659)
  Cases
(n= 878)
Controls
(n= 900)
Cases
(n= 914)
Controls
(n= 967)
Cases
(n= 1,792)
Controls
(n= 1,867)
P-value
Age, yr (Mean ± SD) 51.29 ± 11.38 51.47 ± 11.67 50.11 ± 11.36 48.64 ± 12.28 50.69 ± 11.38 50.01 ± 12.07 0.08
Age group, yr (%)        0.06
< 50 425 (48.41) 463 (51.44) 467 (51.09) 526 (54.40) 896 (49.78) 989 (52.97)  
≥ 50 453 (51.59) 437 (48.56) 447 (48.91) 441 (45.60) 900 (50.22) 878 (47.03)  
Age at menarche, yr (Mean ± SD) 15.26 ± 1.83 15.85 ± 1.89 15.19 ± 1.94 16.23 ± 1.81 15.22 ± 1.89 16.05 ± 1.86 < 0.001
Age at menarche group, yr (%)        < 0.001
< 15 (Early menarche) 331 (38.40) 227 (25.33) 357 (39.98) 169 (17.57) 688 (39.20) 396 (21.31)  
15 to 17 (Normal menarche) 325 (37.70) 352 (39.29) 333 (37.29) 376 (39.09) 658 (37.49) 728 (39.18)  
≥ 17 (Late menarche) 206 (23.90) 317 (35.38) 203 (22.73) 417 (43.35) 409 (23.30) 734 (39.50)  
Age at first live birth, yr (Mean ± SD) 25.62 ± 3.39 24.90 ± 3.35 25.51 ± 3.06 24.17 ± 2.51 25.56 ± 3.22 24.52 ± 2.99 < 0.001d
Age at first live birth group, yr (%) a        < 0.001
< 25 (Early birth) 305 (34.74) 398 (44.27) 312 (34.36) 527 (54.67) 617 (34.55) 925 (49.65)  
≥ 25 a (Late birth) 573 (65.26) 501 (55.73) 596 (65.64) 437 (45.33) 1,169 (65.45) 938 (50.35)  
Age at menopause, yr. (Mean ± SD) b 49.15 ± 4.09 48.90 ± 4.43 48.71 ± 4.63 49.42 ± 4.04 48.93 ± 4.37 49.16 ± 4.25 0.27
Menopausal status (%) b        0.02
Premenopausal 416 (47.38) 437 (48.56) 434 (47.48) 529 (54.71) 850 (47.43) 966 (51.74)  
Postmenopausal 444 (50.57) 448 (49.78) 463 (50.66) 428 (44.26) 907 (50.61) 876 (46.92)  
Estrogen receptor (ER) (%) c        
Positive 369 (42.03)   434 (47.48)   803 (44.81)   
Negative 321 (36.56)   322 (35.23)   643 (35.88)   
Progesterone receptor (PR) (%) c        
Positive 396 (45.10)   414 (45.30)   810 (45.20)   
Negative 294 (33.49)   340 (37.20)   634 (35.38)   
  1. a 10 women (0.27%) without live birth were grouped as "later birth". b Menopause information was available: 907 (51.62%) postmenopausal breast cancer cases and 876 (47.56%) postmenopausal controls. c 1,446 (80.69%) ER status and 1,444 (80.58%) PR status was available in cases. d P-value calculated by t' test for the unequal variances between groups.