Table 2

RRs of breast cancer in relation to percent density and Wolfe classification of prior mammograms

Feature of mammogramNo. of subjectsRRa (95% CI)RRb (95% CI)
CasesControls
Percent densityc
 ≤26.7531181.0 (reference)1.0 (reference)
 26.8–50.1921181.8 (1.2–2.7)1.7 (1.1–2.6)
 50.2–70.21761183.5 (2.3–5.2)3.3 (2.2–5.0)
 ≥70.32261184.4 (3.0–6.7)4.0 (2.7–6.0)
Wolfe classificationd
 N1 and P1641461.0 (reference)1.0 (reference)
 P24203023.2 (2.3–4.5)3.1 (2.2–4.3)
 DY63246.1 (3.5–10.8)5.6 (3.2–10.0)
  • a Adjusted for age and study.

  • b Adjusted for age, study, and mammographic calcifications (see text).

  • c Mean of both breasts, classified into quartiles of controls.

  • d Highest of both breasts.