Table 4 Odds ratio for dense breast among postmenopausal women. In the multivariate analysis, adjusted by age, BMI, smoking status, alcohol status, and hormonal therapy, parity still showed a significant relationship. Compared with women with more than two parity, two parity, single parity and nulliparity had a higher risk of dense breast (OR: 1.849 (95% CI; 1.479–2.312), OR: 3.023 (95% CI; 2.385–3.830), OR: 4.954 (95% CI; 3.975–6.174), respectively)

Age

0.941 (0.933–0.947)

 < 0.001

0.959 (0.952–0.966)

 < 0.001

BMI

0.751 (0.736–0.765)

 < 0.001

0.753 (0.737–0.768)

 < 0.001

Parity

 0

6.322 (5.143–7.772)

 < 0.001

4.954 (3.975–6.174)

 < 0.001

 1

4.013 (3.214–5.012)

 < 0.001

3.023 (2.385–3.830)

 < 0.001

 2

2.124 (1.717–2.628)

 < 0.001

1.849 (1.479–2.312)

 < 0.001

  ≥ 3 (ref)

–

–

–

–

 Trend*

0.565 (0.539–0.592)

 < 0.001

0.575 (0.543–0.610)

 < 0.001

Smoking status

 Never (ref)

–

–

–

–

 Past

1.122 (0.984–1.280)

0.085

1.040 (0.894–1.209)

0.612

 Current

1.385 (1.095–1.753)

0.007

0.946 (0.723–1.238)

0.684

Alcohol status

 Non (ref)

–

–

–

–

 Occasional

1.320 (1.150–1.514)

 < 0.001

1.320 (1.129–1.542)

 < 0.001

 Regular

1.757 (1.589–1.943)

 < 0.001

1.250 (1.113–1.404)

 < 0.001

Family history of breast cancer

1.031 (0.915–1.162)

0.612

–

–

Hormonal therapy

1.355 (1.195–1.536)

 < 0.001

0.975 (0.846–1.123)

0.722