Table 1 Demographic and selected breast cancer risk factors for patients with breast cancer and with BBD

Demographic factors

   Age (years)

48.1 ± 7.4

42.7 ± 6.7

<0.001

   High school education or higher (%)

45.1

49.0

0.555

Known risk factors

   Age at menarche

14.6 ± 1.7

14.7 ± 1.7

0.740

   Postmenopause (%)

35.5

7.4

<0.001

   Age at menopause^b

48.7 ± 4.3

44.6 ± 7.9

0.222

   Breast cancer history among first-degree relatives (%)

4.2

3.1

0.662

   Ever used hormone replacement therapy (%)

3.5

1.0

0.231

   Body mass index (kg/m²)

23.9 ± 3.0

23.3 ± 3.4

0.193

   Waist-to-hip ratio

0.81 ± 0.05

0.79 ± 0.05

0.027

   Ever consumed alcohol (%)

2.8

2.1

0.723

   Physically active during past 10 years (%)

19.0

12.5

0.183