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Table 1 Breast cancer risk factors in the cohort

From: Mammographic density adds accuracy to both the Tyrer-Cuzick and Gail breast cancer risk models in a prospective UK screening cohort

Question Group No breast cancer Breast cancer OR (95 % CI) Univariate summarya Age-adjusted summarya
Age, yr <52 10,601 (21 %) 123 (18 %) 0.85 (0.69–1.04) 58 (52–64)  
  52–64 28,466 (57 %) 387 (56 %) 1.00 (reference) 1.30 (1.14–1.48)  
  >64 10,864 (22 %) 187 (27 %) 1.27 (1.06–1.51) 15.9 (P < 0.001)  
Age at menarche, yr <12 11,298 (23 %) 168 (24 %) 1.09 (0.89–1.31) 13 (12–14)  
  12–13 20,817 (42 %) 285 (41 %) 1.00 (reference) 0.99 (0.90–1.08) 0.99 (0.90–1.08)
  14+ 16,685 (33 %) 230 (33 %) 1.01 (0.84–1.20) 0.1 (P = 0.78) 0.1 (P = 0.77)
  Missing 1131 (2 %) 14 (2 %) 0.90 (0.50–1.49)   
Parous Yes 43,578 (87 %) 591 (85 %) 1.00 (reference)   
  No 6166 (12 %) 103 (15 %) 1.23 (0.99–1.51) 1.23 (0.99–1.51) 1.28 (1.03–1.58)
  Missing 187 (0 %) 3 (0 %) 1.18 (0.29–3.12) 3.6 (P = 0.059) 5.0 (P = 0.026)
Age at birth of first child, yr <21 11,134 (26 %) 139 (24 %) 0.91 (0.74–1.11) 24 (20–27)  
  21–27 21,791 (50 %) 300 (51 %) 1.00 (reference) 1.09 (0.98–1.22) 1.13 (1.01–1.26)
  >27 10,502 (24 %) 150 (25 %) 1.04 (0.85–1.26) 2.4 (P = 0.12) 4.4 (P = 0.037)
  Missing 151 (0 %) 2 (0 %) 0.96 (0.16–3.03)   
Age at menopause, yr <46 16,201 (47 %) 242 (47 %) 0.73 (0.56–0.93) 50 (45–51)  
  46–52 7933 (23 %) 86 (17 %) 1.00 (reference) 1.30 (1.16–1.46) 1.28 (1.14–1.44)
  >52 4906 (14 %) 90 (18 %) 1.23 (0.96–1.56) 21.4 (P < 0.001) 18.4 (P < 0.001)
  Missing 5321 (15 %) 95 (19 %) 1.20 (0.94–1.51)   
BMI, kg/m2 <25 17,538 (35 %) 216 (31 %) 1.00 (reference) 26.5 (23.7–30.4)  
  25–30 16,633 (33 %) 241 (35 %) 1.18 (0.98–1.42) 1.10 (1.01–1.21) 1.11 (1.01–1.21)
  30+ 12,442 (25 %) 192 (28 %) 1.25 (1.03–1.52) 4.6 (P = 0.033) 4.8 (P = 0.028)
  Missing 3318 (7 %) 48 (7 %) 1.17 (0.85–1.59)   
BMI premenopause, kg/m2 <25 1710 (38 %) 18 (31 %) 1.00 (reference) 26.2 (23.3–30.1)  
  25–30 1394 (31 %) 24 (41 %) 1.64 (0.89–3.07) 0.98 (0.71–1.33) 0.98 (0.70–1.32)
  30+ 1087 (24 %) 14 (24 %) 1.22 (0.60–2.46) 0.0 (P = 0.92) 0.0 (P = 0.88)
  Missing 322 (7 %) 3 (5 %) 0.89 (0.21–2.63)   
BMI perimenopause, kg/m2 <25 3176 (36 %) 33 (34 %) 1.00 (reference) 26.4 (23.5–30.3)  
  25–30 2816 (32 %) 33 (34 %) 1.13 (0.69–1.84) 1.00 (0.77–1.27) 1.00 (0.77–1.27)
  30+ 2151 (25 %) 25 (26 %) 1.12 (0.66–1.88) 0.0 (P = 0.99) 0.0 (P = 0.99)
  Missing 601 (7 %) 7 (7 %) 1.12 (0.45–2.40)   
BMI postmenopause, kg/m2 <25 11,918 (35 %) 157 (31 %) 1.00 (reference) 26.5 (23.8–30.4)  
  25–30 11,767 (34 %) 176 (34 %) 1.14 (0.91–1.41) 1.13 (1.02–1.25) 1.14 (1.02–1.26)
  30+ 8603 (25 %) 144 (28 %) 1.27 (1.01–1.60) 5.2 (P =0.023) 5.5 (P = 0.019)
  Missing 2073 (6 %) 36 (7 %) 1.32 (0.90–1.88)   
First-degree relatives with breast cancer 0 44,269 (89 %) 595 (85 %) 1.00 (reference)   
  1 5257 (11 %) 92 (13 %) 1.30 (1.04–1.62) 1.32 (1.09–1.58) 1.30 (1.07–1.56)
  2+ 405 (1 %) 10 (1 %) 1.84 (0.91–3.27) 7.8 (P =0.005) 7.0 (P = 0.008)
Biopsies No 41,311 (83 %) 530 (76 %) 1.00 (reference)   
  Yes 7174 (14 %) 136 (20 %) 1.48 (1.22–1.78) 1.48 (1.22–1.78) 1.45 (1.19–1.75)
  Missing 14,46 (3 %) 31 (4 %) 1.67 (1.14–2.37) 15.0 (P < 0.001) 13.6 (P <0.001)
Current HRT by age group, yr, yes/no <58, no 23,758 (48 %) 286 (41 %) 1.00 (reference)   
  <58, yes 2529 (5 %) 29 (4 %) 0.95 (0.64–1.37) 1.12 (0.82–1.49) 1.43 (1.03–1.95)
  58+, no 22,328 (45 %) 354 (51 %) 1.32 (1.13–1.54) 0.5 (P = 0.47) 4.7 (P = 0.031)
  58+, yes 1316 (3 %) 28 (4 %) 1.77 (1.17–2.57)   
  1. HRT hormone replacement therapy, BMI body mass index, OR odds ratio, CI confidence interval
  2. aSummary, first row: median [interquartile rage (IQR)], second row: IQR odds ratio (95 % confidence interval), third row: likelihood ratio χ2 (P-value)