Table 1. Characteristics of the study population.

	Subcohort (n=382)	Breast cancer cases (n=364)
Age at intake (median, range)	58 (43–66)	58 (41–65)
Age at menopause (median, range)	50 (37–60)	50 (36–60)
Years since menopause (median, range)	7 (0–25)	7 (0–26)
Age at menarche (median, range)	13.3 (10.2–18.0)	13.0 (10.5–18.0)
Nulliparous	81 (21.2%)	65 (17.9%)
If parous: number of children (median, ranged)	3 (1–9)	2 (1–9)
Age at first full-term pregnancy (median, range)	27 (18–42)	27 (16–41)
Positive family history of breast cancera	28 (7.4%)	54 (15.2%)
Ever smoking	99 (25.9%)	91 (25.6%)
Body mass index (kg m−2) (mean, s.d.)	26.1 (4.2)	26.8 (4.1)
Height (cm) (mean, s.d.)	162.1 (6.1)	162.5 (6.2)
Weight (kg) (mean, s.d.)	68.4 (11.1)	70.8 (11.6)
SES
Low	263 (68.8%)	525 (69.2%)
Medium	41 (10.7%)	43 (11.8%)
High	78 (20.4%)	69 (19.0%)
aAt least one first-degree relative with breast cancer.			Percentage of missing values varied from 0 to 1.3% per variable, except for age at menarche, which was only asked in a subgroup (147 breast cancer cases and 198 in subcohort).