Table 1 Characteristics of the study population (n = 907) by smoking status

Age at screening (years)

60.7 (4.4)

61.6 (4.5)

61.9 (4.6)

<0.001

Age at menarche (years)

13.3 (1.4)

13.3 (1.4)

13.3 (1.4)

0.47

Age at first birth^b (years)

22.3 (3.6)

22.7 (3.3)

23.5 (3.9)

<0.001

Number of children^b

2.9 (1.2)

2.8 (1.1)

2.9 (1.4)

0.82

Education (years)

9.4 (3.2)

9.7 (3.4)

10.2 (3.6)

0.02

Age at menopause (years)

47.5 (5.5)

48.8 (4.8)

49.1 (4.8)

<0.001

Body mass index (kg/m²)

26.1 (4.4)

28.4 (5.1)

27.6 (4.7)

<0.001

Alcohol consumption^c (g/day)

3.8 (3.8)

4.0 (3.9)

3.4 (4.0)

0.36

Ever oral contraceptive use (%)

54.8

49.5

37.4

<0.001

Parous (%)

93.6

93.6

90.3

0.13

Ever postmenopausal hormone therapy use (%)

43.2

45.2

41.8

0.72

Breast cancer in first-degree relative (%)

6.8

9.3

9.8

0.18