Table 1. Risk of Benign Breast Diseases by Hormonal Factors.
| Hormonal factor by age groupa | HR (95% CI)b | ||||
|---|---|---|---|---|---|
| Epithelial proliferation | Fibroadenoma | Fibrocystic changes | Cyst | ||
| With atypia | Without atypia | ||||
| Early (<12 y) vs late (>14 y) age at menarche | |||||
| Premenopausal | 0.72 (0.43-1.21) | 1.33 (0.96-1.84) | 0.92 (0.65-1.29) | 0.94 (0.75-1.18) | 0.94 (0.70-1.26) |
| Perimenopausal | 0.67 (0.39-1.15) | 0.61 (0.37-1.02) | 0.78 (0.49-1.22) | 0.94 (0.69-1.28) | 0.90 (0.70-1.16) |
| Postmenopausal | 1.81 (0.80-4.10) | 1.23 (0.56-2.69) | 1.20 (0.36-3.97) | 1.47 (0.76-2.85) | 1.55 (0.91-2.64) |
| Regular vs irregular menstrual cycles | |||||
| Premenopausal | 0.81 (0.57-1.14) | 1.17 (0.88-1.57) | 1.37 (1.02-1.84)c | 1.14 (0.95-1.38) | 1.15 (0.90-1.48) |
| Perimenopausal | 1.05 (0.69-1.59) | 0.85 (0.60-1.20) | 1.27 (0.84-1.94) | 0.99 (0.76-1.28) | 0.96 (0.78-1.19) |
| Postmenopausal | 8.00 (1.11-57.63)c | 0.84 (0.38-1.86) | 0.36 (0.17-0.76)c | 0.67 (0.39-1.14) | 0.99 (0.58-1.69) |
| Short (<27 d) vs long (>30 d) menstrual cycle length | |||||
| Premenopausal | 1.24 (0.75-2.07) | 0.82 (0.57-1.17) | 0.94 (0.67-1.31) | 0.91 (0.72-1.14) | 0.90 (0.66-1.22) |
| Perimenopausal | 1.09 (0.63-1.89) | 1.33 (0.81-2.16) | 0.89 (0.54-1.48) | 1.04 (0.77-1.42) | 0.86 (0.66-1.11) |
| Postmenopausal | 1.53 (0.64-3.67) | 1.48 (0.54-4.04) | 0.28 (0.05-1.55) | 0.92 (0.47-1.78) | 0.85 (0.47-1.54) |
| Nulliparity vs ≥3 children | |||||
| Premenopausal | 0.94 (0.60-1.49) | 0.62 (0.46-0.85)c | 1.19 (0.88-1.61) | 1.05 (0.85-1.29) | 1.38 (1.03-1.85)c |
| Perimenopausal | 1.25 (0.79-1.96) | 1.01 (0.68-1.50) | 1.42 (0.95-2.14) | 1.00 (0.75-1.33) | 0.89 (0.70-1.13) |
| Postmenopausal | 1.18 (0.51-2.73) | 1.41 (0.51-3.87) | 0.25 (0.03-2.07) | 0.78 (0.38-1.60) | 0.76 (0.41-1.39) |
| Older (>32 y) vs young (<23 y) age at first birth | |||||
| Premenopausal | 0.62 (0.36-1.06) | 0.77 (0.54-1.09) | 0.59 (0.40-0.87)c | 1.04 (0.82-1.31) | 1.03 (0.75-1.42) |
| Perimenopausal | 0.82 (0.50-1.35) | 0.97 (0.64-1.46) | 0.78 (0.46-1.32) | 1.23 (0.89-1.72) | 1.05 (0.81-1.35) |
| Postmenopausal | 0.67 (0.24-1.86) | 1.20 (0.38-3.81) | 1.56 (0.50-4.85) | 0.84 (0.39-1.78) | 0.86 (0.42-1.79) |
| Did not breastfeed or short (<3 mo) vs longer (>12 mo) breastfeeding durationd | |||||
| Premenopausal | 1.18 (0.72-1.93) | 0.81 (0.54-1.20) | 1.14 (0.80-1.63) | 1.09 (0.88-1.36) | 0.96 (0.67-1.37) |
| Perimenopausal | 1.12 (0.71-1.79) | 0.98 (0.63-1.53) | 0.60 (0.34-1.07) | 0.71 (0.52-0.96)c | 0.87 (0.67-1.13) |
| Postmenopausal | 1.12 (0.46-2.71) | 1.09 (0.42-2.86) | 0.86 (0.25-2.98) | 0.51 (0.23-1.15) | 0.79 (0.45-1.38) |
| Obese (BMI >30.0) vs normal (BMI of 18.5-25.0) | |||||
| Premenopausal | 0.31 (0.17-0.56)c | 0.74 (0.55-1.00) | 0.56 (0.41-0.78)c | 0.53 (0.43-0.65)c | 0.53 (0.40-0.71)c |
| Perimenopausal | 0.69 (0.46-1.04) | 0.74 (0.51-1.07) | 1.05 (0.73-1.50) | 0.48 (0.35-0.65)c | 0.43 (0.33-0.56)c |
| Postmenopausal | 0.66 (0.29-1.48) | 1.29 (0.64-2.60) | 0.57 (0.17-1.90) | 0.93 (0.51-1.73) | 0.52 (0.30-0.89)c |
Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); HR, hazard ratio.
a
Premenopausal ages are 25 to 44 years; perimenopausal ages, 45 to 54 years; and postmenopausal ages, 55 to 69 years.
b
Cox proportional hazards regression with time-varying covariates using age as the time scale adjusted for Karolinska Mammography Project for Risk Prediction of Breast Cancer unit, birth cohort, and educational level.
c
Significant association at P < .05.
d
Breastfeeding duration analyzed in parous women only.