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Table 3 Association between mammographic density and other selected risk factors, and risk of total breast cancer stratified by means of detection in the NBCSP case-control study

From: Mammographic density and risk of breast cancer according to tumor characteristics and mode of detection: a Spanish population-based case-control study

   Screen-detected breast cancer   Interval breast cancer
Baseline risk factor No. of controls (%) No. of cases (%) Odds ratioa(95% CI)   No. of cases (%) Odds ratioa(95% CI)
Age at first live birthb       
   5-year increase 4,048 (86.8) 705 (81.0) 1.11 (1.00-1.23)   202 (84.2) 1.17 (0.98-1.41)
   Nulliparous 618 (13.2) 165 (19.0) 1.38 (1.12-1.70)   38 (15.8) 1.14 (0.77-1.70)
Age at menopausec       
   5-year increase 3,040 (65.2) 573 (65.9) 1.17 (1.05-1.31)   121 (50.4) 1.18 (0.92-1.50)
   Premenopausal 1,626 (34.8) 297 (34.1) 1.04 (0.82-1.32)   119 (49.6) 1.56 (1.02-2.38)
Family history of breast cancer       
   None 4,055 (86.9) 712 (81.8) 1.00 (reference)   184 (76.7) 1.00 (reference)
   Second-degree relative 325 (7.0) 75 (8.6) 1.24 (0.95-1.63)   28 (11.7) 1.83 (1.16-2.87)
   First-degree relative ≥50 years 172 (3.7) 49 (5.6) 1.49 (1.06-2.10)   13 (5.4) 1.55 (0.80-2.97)
   First-degree relative <50 years 114 (2.4) 34 (3.9) 1.57 (1.05-2.36)   15 (6.3) 2.83 (1.53-5.22)
Previous breast biopsy       
   No 4,263 (91.4) 747 (85.9) 1.00 (reference)   200 (83.3) 1.00 (reference)
   Yes 403 (8.6) 123 (14.1) 1.48 (1.18-1.86)   40 (16.7) 1.99 (1.34-2.96)
Mammographic density (%)       
   0-10 1,710 (36.6) 220 (25.3) 1.00 (reference)   32 (13.3) 1.00 (reference)
   11-25 1,136 (24.3) 188 (21.6) 1.30 (1.05-1.62)   46 (19.2) 1.95 (1.20-3.17)
   26-50 1,157 (24.8) 273 (31.4) 2.00 (1.62-2.47)   87 (36.3) 3.54 (2.24-5.60)
   51-75 528 (11.3) 155 (17.8) 2.45 (1.89-3.17)   52 (21.7) 4.25 (2.53-7.14)
   >75 135 (2.9) 34 (3.9) 2.17 (1.40-3.36)   23 (9.6) 7.72 (4.02-14.81)
   P value for trendd    <0.001    < 0.001
  1. aOdds ratios and 95% confidence intervals (CIs) for screen-detected and interval breast cancer obtained from separate multivariate conditional logistic regression models adjusted for all risk factors shown in the table. bAdjusted odds ratios per 5-year increase in age at first live birth among parous women, as well as for nulliparous women compared with women having their first live birth at 25 years. cAdjusted odds ratios per 5-year increase in age at menopause among postmenopausal women, as well as for premenopausal women compared with women having their menopause at 45 years. dP values for linear trend by using an ordinal variable with values 1 through 6 across successive categories of mammographic density.