From: Active smoking and risk of breast cancer in a Danish nurse cohort study
Total N = 21,831 | Breast Cancer N = 1162 | No Breast Cancer N = 20,669 | |
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Age | |||
Mean (SD) age at baseline (years) | 53.2 (8.0) | 53.7 (7.6) | 53.2 (8.1) |
Birth Cohort | |||
Born 1900–1934, n (%) | 5179 (23.7) | 295 (25.4) | 4884 (23.6) |
Born 1935–1944, n (%) | 6707 (30.7) | 428 (36.8) | 6279 (30.4) |
Born 1945–1949, n (%) | 4564 (20.9) | 244 (21.0) | 4320 (20.9) |
Born 1950–1955, n (%) | 5381 (24.6) | 195 (16.8) | 5186 (25.1) |
Reproductive Factors | |||
Mean (SD) age at menarche | 13.5 (1.5) | 13.5 (1.5) | 13.5 (1.5) |
Nulliparous, n (%) | 3170 (14.5) | 189 (16.3) | 2981 (14.4) |
Mean (SD) number of children in parous women | 2.3 (0.9) | 2.3 (0.9) | 2.3 (0.9) |
Mean (SD) age at first birth in parous women | 25.9 (4.0) | 25.9 (4.0) | 26.3 (4.1) |
Postmenopausal, n (%) | 12,376 (56.7) | 696 (59.9) | 11,680 (56.5) |
Body Mass Index (BMI) | |||
Mean (SD) BMI (kg/m2) | 23.7 (3.5) | 23.8 (3.5) | 23.7 (3.5) |
BMI < 18.5 kg/m2, n (%) | 529 (2.4) | 22 (1.9) | 507 (2.5) |
BMI 18.5–24.9 kg/m2, n (%) | 15,070 (69.0) | 819 (70.5) | 14,251 (68.9) |
BMI 25–29.9 kg/m2, n (%) | 4979 (22.8) | 245 (21.1) | 4734 (22.9) |
BMI ≥ 30 kg/m2, n (%) | 1253 (5.7) | 76 (6.5) | 1177 (5.7) |
Alcohol consumption | |||
Does not drink alcohol, n (%) | 3320 (15.2) | 183 (15.7) | 3137 (15.2) |
Moderate drinker (1–14 drinks/week), n (%) | 13,533 (62.0) | 670 (57.7) | 12,863 (62.2) |
Heavy drinker (> 14 drinks/week), n (%) | 4978 (22.8) | 309 (26.6) | 4669 (22.6) |
Leisure time physical activity | |||
Low physical activity, n (%) | 1428 (6.5) | 79 (6.8) | 1349 (6.5) |
Medium physical activity, n (%) | 5905 (27.0) | 298 (25.6) | 5607 (27.1) |
High physical activity, n (%) | 14,498 (66.4) | 785 (67.6) | 13,713 (66.3) |
Shift Work | |||
Working night shifts, n (%) | 967 (5.5) | 45 (4.9) | 922 (5.5) |
Hormone Use | |||
Ever used oral contraceptives, n (%) | 12,701 (58.2) | 663 (57.1) | 12,038 (58.2) |
Ever used hormone therapy, n (%) | 5951 (27.3) | 407 (35.0) | 5544 (26.8) |
Smoking Status | |||
Never smoker, n (%) | 7923 (36.3) | 379 (32.6) | 7544 (36.5) |
Former smoker, n (%) | 6557 (30.0) | 338 (29.1) | 6219 (30.1) |
Current smoker, n (%) | 7351 (33.7) | 445 (38.3) | 6906 (33.4) |
Ever smoker, n (%) | 13,908 (63.7) | 783 (67.4) | 13,125 (63.5) |
Smoking Intensity | |||
Mean (SD) smoking durationa (years) | 23.3 (12.2) | 23.9 (11.7) | 23.3 (12.2) |
Mean (SD) smoking intensitya (g/day) | 12.4 (8.3) | 12.7 (8.0) | 12.4 (8.3) |
Mean (SD) pack-yearsa | 16.0 (14.8) | 16.6 (14.8) | 15.9 (14.8) |
Initiation of smoking | |||
Mean age (SD) at smoking initiationa (years) | 20.4 (5.5) | 20.7 (5.7) | 20.4 (5.5) |
Initiation of smoking in 18,661 parous women | |||
Parous never smoker | 6938 (37.2) | 326 (33.5) | 6612 (37.4) |
Parous ever smoker | 11,723 (62.8) | 647 (66.5) | 11,076 (62.6) |
Parous/around 1st birth or later, n (%) | 1457 (6.7) | 88 (7.6) | 1369 (6.6) |
Parous/before 1st childbirth, ≤ 10 pack-years, n (%) | 9367 (42.9) | 493 (42.4) | 8874 (42.9) |
Parous/before 1st childbirth, > 10 pack-years, n (%) | 899 (4.1) | 66 (5.7) | 833 (4.0) |
Initiation of smoking in 3170 nulliparous women | |||
Nulliparous never smoker | 985 (31.1) | 53 (28.0) | 932 (31.3) |
Nulliparous ever smoker | 2185 (68.9) | 136 (72.0) | 2049 (68.7) |
Nulliparous, before age 21b years, n (%) | 1264 (5.8) | 74 (6.4) | 1190 (5.8) |
Nulliparous, age 21 years or later, n (%) | 921 (4.2) | 62 (5.3) | 859 (4.2) |
Initiation of smoking in 12,376 postmenopausal women | |||
Postmenopausal never smoker, n (%) | 3988 (32.2) | 202 (29.0) | 3786 (32.4) |
Before menopause, n (%) | 8301 (67.1) | 488 (70.1) | 7813 (66.9) |
After menopause, n (%) | 87 (0.7) | 6 (0.9) | 81 (0.7) |