Table 1. Descriptive characteristics of all cases and controls.

Characteristic	Cases (%), n=639	Controls (%), n=640	P-value
Socioeconomic status
Professional	157 (25)	170 (27)	0.71
Nonmanual	219 (34)	212 (33)
Manual/not employed	263 (41)	258 (40)
Use of oral contraceptives
Never	110 (17)	130 (20)	0.37
Last use <5 years ago	117 (18)	112 (18)
Last use⩾5 years ago	412 (64)	398 (62)
Alcohol consumption
Non-drinkers	210 (33)	206 (32)	0.89
1–50 g week−1	261 (41)	270 (42)
50+ g week−1	168 (26)	164 (26)
History of breast cancer in first-degree relative
No	557 (87)	585 (91)	0.02
Yes	71 (11)	43 (7)
N/K	11 (2)	12 (2)
Mean height (cm)	163.8	163.1	0.06
Mean weight (kg)	62.5	63.5	0.09
Mean BMI (kg m−2)	23.3	23.9	0.01
Mean age at menarche (years)	12.5	12.6	0.16
Parity
Nulliparous	93 (15)	79 (12)	0.25
Parous	546 (85)	561 (88)
Mean age at first giving birth (years) (among parous)	24.4	24.1	0.30
Menopausal status
Premenopausal	591 (92)	595 (93)	0.74
Peri/postmenopausal	48 (8)	45 (7)
Active smoking exposure
Never	297 (46)	310 (48)
Past	156 (24)	144 (23)
Mean cigarettes per day	11.3	10.7
Mean years smoked	10.8	10.6
Mean age started smoking	17.8	17.7
Current	186 (29)	186 (29)
Mean cigarettes per day	14.0	14.1
Mean years smoked	23.2	22.6
Mean age started smoking	17.6	17.7
Active and passive exposure
Never smoker, no passive exposure	175 (27)	175 (27)
Never smoker, passive exposure	122 (19)	135 (21)
Mean years of exposure	12.2	13.3
Past smoker, no passive exposure	58 (9)	52 (8)
Past smoker, passive exposure	98 (15)	92 (14)
Mean years of exposure	12.0	12.9
Current smoker, no passive exposure	44 (7)	38 (6)
Current smoker, passive exposure	142 (22)	148 (23)
Mean years of exposure	16.2	14.8