From: Active smoking and risk of breast cancer in a Danish nurse cohort study
N | Person-years | No. of cases | Age adjusted | Fullya adjusted | |
---|---|---|---|---|---|
HR (95% CI) | HR (95% CI) | ||||
Never smoked (ref.) | 7923 | 126,950 | 379 | 1.00 | 1.00 |
Former smoker | 6557 | 102,190 | 338 | 1.11 (0.96–1.29) | 1.08 (0.94–1.26) |
Current smoker | 7351 | 113,400 | 445 | 1.32 (1.15–1.51) | 1.27 (1.11–1.46) |
Ever smokers | 13,908 | 215,589 | 783 | 1.22 (1.08–1.38) | 1.18 (1.04–1.34) |
Smoking duration among ever smokers | |||||
≤ 10 years | 2925 | 47,335 | 156 | 1.10 (0.92–1.33) | 1.10 (0.91–1.33) |
11–20 years | 3175 | 50,151 | 175 | 1.17 (0.98–1,40) | 1.15 (0.96–1.38) |
21–30 years | 4456 | 68,818 | 259 | 1.26 (1.08–1.48) | 1.24 (1.06–1.46) |
> 30 years | 3295 | 49,285 | 193 | 1.32 (1.11–1.57) | 1.21 (1.01–1.46) |
p-value for trend | 0.004 | ||||
Every increase of 10 years | 1.08 (1.04–1.12) | 1.06 (1.02–1-11) | |||
Smoking (Tobacco) Intensity among ever smokers | |||||
> 6 g/day | 3098 | 49,245 | 161 | 1.10 (0.91–1.32) | 1.07 (0.89–1.29) |
6–10 g/day | 4317 | 67,410 | 235 | 1.17 (0.99–1.38) | 1.14 (0.97–1.34) |
11–15 g/day | 3050 | 46,962 | 175 | 1.25 (1.05–1.50) | 1.22 (1.02–1.46) |
> 15 g/day | 3443 | 51,973 | 212 | 1.37 (1.16–1.62) | 1.31 (1.11–1.56) |
p-value for trend | 0.001 | ||||
Every increase of 10 g/day | 1.05 (0.97–1.14) | 1.04 (0.95–1.13) | |||
Lifetime pack-years | |||||
≤ 10 pack-years | 6082 | 96,640 | 327 | 1.13 (0.98–1.31) | 1.12 (0.97–1.30) |
11–20 pack-years | 3536 | 54,993 | 192 | 1.17 (0.99–1.39) | 1.14 (0.96–1.36) |
> 20 pack-years | 4290 | 63,956 | 264 | 1.39 (1.19–1.63) | 1.32 (1.12–1.55) |
p-value for trend | 0.002 | ||||
Every increase of 20 pack-years | 1.10 (1.01–1.20) | 1.07 (0.98–1.18) | |||
Initiation of smoking in 18,661 parous women | |||||
Parous never smoker (ref.) | 6938 | 111,811 | 326 | 1.00 | 1.00 |
Parous, around first birth or later | 1457 | 23,553 | 88 | 1.28 (1.01–1.62) | 1.28 (1.00–1.62) |
Parous, before first childbirth, ≤ 10 pack-years | 9367 | 146,965 | 493 | 1.15 (1.00–1.33) | 1.13 (0.98–1.31) |
Parous, before first childbirth, > 10 pack-years | 899 | 12,901 | 66 | 1.77 (1.36–2-31) | 1.58 (1.20–2.10) |
Initiation of smoking in 3170 nulliparous women | |||||
Nulliparous never smoker (ref.) | 985 | 15,138 | 53 | 1.00 | 1.00 |
Nulliparous, before age 21b years | 1264 | 18,737 | 74 | 1.14 (0.80–1.62) | 1.10 (0.76–1.58) |
Nulliparous, age 21 years or later | 921 | 13,434 | 62 | 1.31 (0.91–1.90) | 1.29 (0.89–1.88) |
Initiation of smoking in 12,376 postmenopausal women | |||||
Postmenopausal never smoker (ref.) | 3988 | 66,617 | 202 | 1.00 | 1.00 |
Before menopause | 8301 | 130,987 | 488 | 1.23 (1.05–1.45) | 1.20 (1.01–1.41) |
After menopause | 87 | 1252 | 6 | 1.60 (0.71–3.59) | 1.66 (0.74–3.75) |
Pack-years in 8347 parous postmenopausal womenc | |||||
Parous postmenopausal never smoker (ref.) | 2712 | 129 | 1.00 | 1.00 | |
Pack-years before 1st childbirthd | |||||
≤ 10 pack-years | 4349 | 70,627 | 227 | 1.16 (0.93–1.44) | 1.14 (0.92–1.42) |
11–20 pack-years | 366 | 5233 | 34 | 2.36 (1.62–3.45) | 2.16 (1.45–3.20) |
> 20 pack-years | 61 | 854 | 4 | 1.69 (0.63–4.59) | 1.38 (0.50–3.78) |
p-value for trend | 0.006 | ||||
Pack-years from 1st childbirth until menopaused | |||||
≤ 10 pack-years | 2572 | 42,484 | 128 | 1.08 (0.85–1.38) | 1.03 (0.81–1.33) |
11–20 pack-years | 1606 | 25,391 | 79 | 1.12 (0.85–1.49) | 1.13 (0.85–1.50) |
> 20 pack-years | 817 | 12,471 | 60 | 1.74 (1.28–2.36) | 1.84 (1.34–2.53) |
p-value for trend | 0.029 | ||||
Pack-years after menopaused | |||||
≤ 10 pack-years | 2294 | 37,270 | 124 | 1.20 (0.94–1.53) | 1.19 (0.93–1.53) |
11–20 pack-years | 453 | 6695 | 20 | 1.09 (0.68–1.74) | 1.03 (0.64–1.66) |
> 20 pack-years | 1966 | 32,094 | 118 | 1.32 (1.03–1.70) | 1.29 (0.70–4.98) |
p-value for trend | 0.412 |