Table 1. Selected characteristics of women by smoking status at enrolment, Norwegian Women and Cancer Study, 1991–2012 (N=130 053).
|
Never smokers |
Passive smokers |
Ever (former and current) smokers |
||||
|---|---|---|---|---|---|---|
| Characteristics | N (%) | Mean (±s.d.) | N (%) | Mean (±s.d.) | N (%) | Mean (±s.d.) |
| Women | 14 867 (11.4) | 27 342 (21.0) | 87 844 (67.5) | |||
| Age at enrolment | 50.7 (8.7) | 49.0 (8.2) | 48.5 (8.0) | |||
| Person-years | 200 397 (11.5) | 379 082 (21.7) | 1 168 105 (66.8) | |||
| Follow-up years | 13.5 (6.1) | 13.9 (6.3) | 13.3 (6.3) | |||
| Primary invasive breast cancers | 411 (9.9) | 908 (22.0) | 2813 (68.1) | |||
| Age at diagnosis | 58.9 (7.6) | 57.6 (7.6) | 56.8 (7.3) | |||
| Diagnosis before age 50 years | 55 (13.4) | 154 (17.0) | 522 (18.6) | |||
| Premenopausal breast cancer | 57 (13.9) | 162 (17.8) | 519 (18.5) | |||
| Family history of breast cancer | 818 (5.5) | 1476 (5.4) | 4568 (5.2) | |||
| Higher education ⩾13 years | 7909 (53.2) | 13 835 (50.6) | 34 347 (39.1) | |||
| Age at menarche | 13.3 (1.4) | 13.3 (1.4) | 13.3 (1.4) | |||
| Age at menopause | 49.4 (4.5) | 49.1 (4.7) | 48.2 (4.9) | |||
| Ever hormonal contraceptive use | 6452 (43.4) | 14 464 (52.9) | 54 815 (62.4) | |||
| Parous women | 13 157 (88.5) | 24 799 (90.7) | 80 026 (91.1) | |||
| Number of children | 2.4 (1.4) | 2.3 (1.2) | 2.1 (1.1) | |||
| Age at first childbirth | 25.1 (4.3) | 24.6 (4.3) | 23.6 (4.4) | |||
| Postmenopausal | 6185 (41.6) | 2788 (35.8) | 32 151 (36.6) | |||
| Ever postmenopausal hormone use | 3196 (21.5) | 5824 (21.3) | 21 961 (25.0) | |||
| Non-drinkers | 3910 (26.3) | 3855 (14.1) | 4480 (5.1) | |||
| Alcohol consumption (g per day)a | 2.0 (3.5) | 2.8 (4.0) | 4.0 (5.6) | |||
| BMI (kg m−2)b | 24.3 (3.9) | 24.4 (4.0) | 24.1 (3.9) | |||
| Physical activity scorec | 5.8 (1.8) | 5.7 (1.8) | 5.7 (1.9) | |||
Abbreviation: s.d.=standard deviation.
a
Among women who consumed alcohol, expressed in grams per day.
b
Body mass index; weight in kilograms divided by the square of the heights in metres.
c
Physical activity score in 10 categories.