Table 1 Descriptive characteristics of 104 premenopausal women with invasive (n = 88) or in situ (n = 10) breast cancer and 225 matched controls; baseline values

Age, year; mean (SD)

43.5 (4.3)

43.3 (4.0)

-0.06 - 0.46

0.134

Age at menarche, year;

median (interquartile range)

13 (12;14)

12.5 (12;13.3)

-1.0 - 0.0

0.723^a

Parity (parous women only); median (interquartile range)

2 (1.0;2.0)

2 (1.1;2.3)

-0.25 - 0.25

0.640^a

Age at first birth (parous women only); median (rnterquartile range)

24.8 (22.3;28.3)

24.3 (21.8;26.1)

-2.79 - 0.69

0.229^a

BMI, kg/m²; mean (SD)

25.0 (4.5)

25.2 (3.4)

-1.28 - 0.91

0.733

Alcohol consumption, g/d;

mean (SD)

1.7 (1.3)

1.5 (1.1)

-0.25 - 0.70

0.346

Pack-years, ever smokers; mean (SD)

7.8 (5.9)

10.2 (10.0)

-6.48 - 1.64

0.230

χ ²

P value

Breastfeeding; n (%)

73 (70.2)

166 (73.8)

0.354

OC use; n (%)

43 (41.3)

92 (40.9)

0.350

Education beyond 8 years

of elementary school; n (%)

68 (65.4)

119 (52.9)

0.001

Current smoker; n (%)

22 (21.2)

44 (19.6)

0.387

Past smoker; n (%)

19 (18.3)

24 (10.7)

0.019

Never smoker; n (%)

63 (60.6)

157 (69.8)

0.860