Table 2.

Risk of breast cancer according to quintiles of percent and absolute density for all subjects (n = 1,020)

Quintile of percent density
P*Quintile of absolute density
P*
1234512345
Percent dense volume (%)Dense volume (cm3)
No. of cases62647578856468618685
No. of controls142140129126119140136143118119
OR unadjusted (95% CI)Reference1.05 (0.7, 1.6)1.33 (0.9, 2.0)1.42 (0.9, 2.1)1.64 (1.1, 2.5)0.01Reference1.09 (0.7, 1.7)0.93 (0.6, 1.4)1.59 (1.1, 2.4)1.56 (1.0, 2.3)0.1
OR adjusted for risk factors (95% CI)Reference1.08 (0.7, 1.6)1.39 (0.9, 2.1)1.60 (1.0, 2.5)1.98 (1.3, 3.1)0.001Reference1.10 (0.7, 1.7)0.98 (0.6, 1.5)1.69 (1.1, 2.6)1.68 (1.1, 2.6)0.003
Percent dense area (%)Dense area (cm2)
No. of cases70607676827162697884
No. of controls134144128128122133142135126120
OR unadjusted (95% CI)Reference0.80 (0.5, 1.2)1.14 (0.8, 1.8)1.14 (0.8, 1.7)1.29 (0.9, 1.9)0.06Reference0.82 (0.5, 1.2)0.96 (0.6, 1.4)1.16 (0.8, 1.7)1.31 (0.9, 2.0)0.05
OR adjusted for risk factors (95% CI)Reference0.92 (0.6, 1.4)1.41 (0.9, 2.2)1.49 (0.9, 2.3)1.86 (1.1, 3.0)0.003Reference0.90 (0.6, 1.4)1.07 (0.7, 1.6)1.29 (0.8, 2.0)1.48 (1.0, 2.3)0.02
• NOTE: Shown are mean (SD) and percentage for, respectively, continuous and categorical variables.

• * Unconditional logistic regression analysis. P value is from a test of linear trend with quintiles as an ordinary variable in the model.

• Age at mammogram (y), age at first birth (y), weight (kg), height (cm), menopausal status (premenopausal, postmenopausal), and parity (parous, nonparous).