Table 1. Odds Ratios for Breast Cancer According to Risk Factors, Collaborative Breast Cancer Study, 1988-2008.
Characteristic | Cases (n=23,959) % | Controls (n=28,304) % | Odds Ratioa | 95% CIa | Effect Modification P-value | |
---|---|---|---|---|---|---|
with Ageb | with Menopausal Statusc | |||||
First degree family history of breast cancer | ||||||
None | 78.2 | 85.8 | 1 | 0.01 | 0.001 | |
1 | 17.3 | 11.5 | 1.61 | 1.53-1.69 | ||
2 | 2.2 | 0.9 | 2.44 | 2.10-2.84 | ||
≥ 3 | 0.3 | 0.1 | 3.04 | 1.97-4.69 | ||
Unknown | 2.0 | 1.7 | ||||
None | 78.2 | 85.8 | 1 | 0.001 | 0.001 | |
1, diagnosed < 50 yr | 5.0 | 3.1 | 1.74 | 1.59-1.90 | ||
1, diagnosed 50-59 yr | 4.0 | 2.7 | 1.61 | 1.46-1.78 | ||
1, diagnosed ≥ 60 yr | 7.9 | 5.4 | 1.55 | 1.44-1.66 | ||
≥ 2, diagnosed <50 yr | 1.4 | 0.6 | 2.62 | 2.16-3.17 | ||
≥ 2, diagnosed ≥50 yr | 1.1 | 0.5 | 2.49 | 2.02-3.07 | ||
Unknown | 2.5 | 2.0 | ||||
Benign breast disease | n=14,144 h | n=15,830 h | ||||
Never | 72.0 | 79.7 | 1 | 0.14 | 0.15 | |
Ever | 26.0 | 18.5 | 1.61 | 1.53-1.71 | ||
Unknown | 2.0 | 1.8 | ||||
Age at menarche | ||||||
≤ 12 | 43.9 | 41.5 | 1 | 0.42 | 0.75 | |
13 | 27.2 | 27.2 | 0.94 | 0.90-0.98 | ||
14 | 15.1 | 16.0 | 0.88 | 0.84-0.93 | ||
≥ 15 | 11.4 | 13.2 | 0.80 | 0.76-0.85 | ||
Unknown | 2.4 | 2.2 | ||||
Parity | ||||||
Nulliparous | 13.5 | 12.0 | 1 | 0.0001 | 0.11 | |
Parous | 85.7 | 87.4 | 0.84 | 0.80-0.89 | ||
Unknown | 0.8 | 0.7 | ||||
Parity | ||||||
0 | 13.5 | 11.9 | 1 | 0.06 | 0.33 | |
1 | 11.2 | 10.1 | 0.99 | 0.92-1.07 | ||
2 | 29.2 | 27.2 | 0.94 | 0.90-1.00 | ||
≥ 3 | 45.4 | 50.2 | 0.75 | 0.71-0.80 | ||
Unknown | 0.8 | 0.7 | ||||
Age at first full term pregnancy (years) | ||||||
< 22 | 29.8 | 34.5 | 1.00 | 0.30 d | 0.26 d | |
22-24 | 23.2 | 24.3 | 1.12 | 1.07-1.17 | ||
25-29 | 22.5 | 20.6 | 1.30 | 1.24-1.36 | ||
≥ 30 | 10.2 | 8.0 | 1.52 | 1.43-1.63 | ||
Nulliparous | 13.5 | 12.0 | 1.37 | 1.29-1.45 | ||
Unknown | 0.9 | 0.7 | ||||
Breastfeeding (parous women only) | ||||||
Never | 49.4 | 49.3 | 1 | 0.94 | 0.87 | |
Ever | 50.6 | 50.7 | 0.97 | 0.94, 1.01 | ||
Breastfeeding duration (parous women only) | ||||||
Never | 49.4 | 49.3 | 1 | 0.75 | 0.04 | |
≤ 12 months | 36.3 | 35.8 | 0.98 | 0.94-1.03 | ||
> 12 months | 14.1 | 14.7 | 0.95 | 0.89-1.00 | ||
Unknown | 0.2 | 0.2 | ||||
Oral contraceptive usee | ||||||
Never | 54.9 | 54.7 | 1.00 | <0.0001 | 0.19 | |
Ever | 44.1 | 44.3 | 1.05 | 1.01-1.10 | ||
Unknown | 1.1 | 1.0 | ||||
Body mass index (kg/m2) | ||||||
< 18.5 (underweight) | 1.8 | 2.4 | 0.79 | 0.70-0.90 | <0.0001 | <0.0001 |
18.5 –24.9 (normal) | 46.8 | 48.9 | 1 | |||
25 –29.9 (overweight) | 30.0 | 29.3 | 1.02 | 0.98-1.06 | ||
≥ 30 (obese) | 19.2 | 17.2 | 1.09 | 1.03-1.14 | ||
Unknown | 2.2 | 2.2 | ||||
Smoking statusg | ||||||
Never | 49.0 | 49.1 | 1 | 0.03 | 0.38 | |
Former | 30.3 | 28.8 | 1.04 | 1.00-1.08 | ||
Current | 19.8 | 21.3 | 0.96 | 0.91-1.00 | ||
Unknown | 0.9 | 0.8 | ||||
Recent alcohol consumption (drinks/week) | n=18,895 h | n=23,028 h | ||||
Never | 10.2 | 11.7 | 1.00 | 0.0002 | 0.0004 | |
Former | 9.4 | 8.8 | 1.16 | 1.07-1.27 | ||
< 7 | 63.0 | 64.8 | 1.11 | 1.04-1.19 | ||
7-13 | 9.6 | 8.8 | 1.25 | 1.15-1.37 | ||
≥ 14 | 6.0 | 4.2 | 1.65 | 1.48-1.83 | ||
Unknown | 1.8 | 1.8 |
Odds ratios are age-adjusted for age, state of residence, and study period.
Age defined continuously (per year)
Excludes women with unknown menopausal status
Parous women only
Odds ratio adjusted for residuals of time since last use regressed on age (instead of adjusted for age).
Excludes women who never used oral contraceptive.
Odds ratios are age-adjusted for age, state of residence, study period, body mass index, and alcohol consumption.
Sample sizes are shown when a reduced number of women are included in the analysis.