From: Risk factors for ductal and lobular breast cancer: results from the nurses' health study
 | Ductal (n= 4,655) | Lobular (n= 659) |  | ||
---|---|---|---|---|---|
Reproductive or hormonal exposures | Cases (n) | RR (95% CI) | Cases (n) | RR (95% CI) | P-heterogeneityb |
Age (per year)c | 1,947 | 1.03 (1.02-1.04) | 286 | 1.04 (1.02-1.06) | 0.71 |
Age at menarche (per year)c | 1,947 | 0.99 (0.96-1.02) | 286 | 0.87 (0.80-0.95) | 0.005 |
Parous | 1,795 | 1.00 (ref) | 276 | 1.00 (ref) | Â |
Nulliparous | 200 | 1.17 (0.94-1.47) | 17 | 0.90 (0.47-1.72) | 0.45 |
Age at first birth (AFB) | Â | Â | Â | Â | Â |
   AFB < 25 | 1,040 | 1.00 (ref) | 111 | 1.00 (ref) |  |
   AFB 25-29 | 730 | 1.06 (0.95-1.17) | 131 | 1.82 (1.39-2.38) |  |
   AFB 30-34 | 174 | 1.09 (0.92-1.29) | 41 | 2.62 (1.78-3.88) |  |
   AFB ≥35 | 51 | 1.02 (0.76-1.37) | 10 | 2.10 (1.04-4.21) | <0.001 |
   AFB, continuous, RR (P trend)c |  | 1.11 (0.004) |  | 1.56 (<0.001) | <0.001 |
Parity | Â | Â | Â | Â | Â |
   Parity = 1 | 360 | 1.00 (ref) | 48 | 1.00 (ref) |  |
   Parity = 2 | 476 | 0.82 (0.68-0.99) | 72 | 0.71 (0.46-1.10) |  |
   Parity = 3 | 545 | 0.90 (0.75-1.08) | 69 | 0.71 (0.45-1.11) |  |
   Parity ≥ 4 | 614 | 0.80 (0.67-0.97) | 104 | 0.94 (0.61-1.46) | 0.09 |
   Parity, continuous, RR (P trend)d |  | 0.98 (0.15) |  | 1.06 (0.12) | 0.05 |
Postmenopausal hormone use | Â | Â | Â | Â | Â |
   Never used | 738 | 1.00 (ref) | 90 | 1.00 (ref) |  |
   Past use | 549 | 1.09 (0.97-1.22) | 73 | 1.18 (0.85-1.63) |  |
   Current use, estrogen alone < 5 years | 59 | 1.01 (0.77-1.32) | 12 | 1.64 (0.88-3.05) |  |
   Current use, estrogen plus progesterone < 5 years | 155 | 1.74 (1.45-2.08) | 29 | 2.95 (1.90-4.57) |  |
   Current use, other ≤10 years | 91 | 1.28 (1.03-1.59) | 14 | 1.82 (1.05-3.17) |  |
   Current use, estrogen alone 5-10 years | 118 | 1.36 (1.11-1.67) | 26 | 2.49 (1.57-3.97) |  |
   Current use, estrogen + progesterone 5-10 years | 180 | 2.05 (1.73-2.43) | 35 | 3.37 (2.23-5.08) | <0.001 |
   Estrogen alone, continuous, RR (P trend)e |  | 1.00 (0.006) |  | 1.00 (0.63) | 0.53 |
   Estrogen + progesterone, continuous, RR (P trend)e |  | 1.03 (<0.001) |  | 1.03 (<0.001) | 0.24 |
   Other, continuous, RR (P trend)e |  | 1.00 (0.71) |  | 1.01 (0.36) | 0.44 |
Age at menopause (per year)c | 1,947 | 1.00 (1.00-1.01) | 286 | 1.02 (1.00-1.03) | 0.16 |
Menopausal type | Â | Â | Â | Â | Â |
   Natural or radiation-induced | 1,337 | 1.00 (ref) | 185 | 1.00 (ref) |  |
   Surgical with two ovaries removed | 194 | 0.75 (0.64-0.88) | 29 | 0.89 (0.59-1.36) |  |
   Surgical with one or no ovaries removed | 202 | 0.86 (0.73-1.00) | 35 | 1.10 (0.75-1.60) | 0.63 |
Nonreproductive exposures | Â | Â | Â | Â | Â |
Body mass index (BMI) | Â | Â | Â | Â | Â |
   <21 | 178 | 1.00 (ref) | 26 | 1.00 (ref) |  |
   21 to less than 23 | 251 | 1.05 (0.87-1.27) | 37 | 1.08 (0.66-1.78) |  |
   23 to less than 25 | 347 | 1.27 (1.06-1.52) | 51 | 1.32 (0.82-2.11) |  |
   25 to less than 30 | 677 | 1.54 (1.30-1.82) | 98 | 1.49 (0.96-2.31) |  |
   ≥30 | 465 | 2.00 (1.67-2.39) | 67 | 1.87 (1.16-3.01) | 0.23 |
   BMI, continuous, RR (P trend)f |  | 1.23 (<0.001) |  | 1.25 (<0.001) | 0.79 |
BMI at age 18 | Â | Â | Â | Â | Â |
   <19 | 355 | 1.18 (1.04-1.35) | 51 | 1.42 (0.97-2.01) |  |
   19 to less than 21 | 593 | 1.00 (ref) | 76 | 1.00 (ref) |  |
   21 to less than 23 | 399 | 0.84 (0.74-0.95) | 71 | 1.22 (0.89-1.67) |  |
   ≥23 | 354 | 0.81 (0.71-0.93) | 49 | 0.89 (0.61-1.30) | 0.03 |
   BMI at age 18, continuous, RR (P trend)f |  | 0.80 (<0.001) |  | 0.81 (0.08) | 0.95 |
Alcohol intake (g/day) | Â | Â | Â | Â | Â |
   0 | 1,062 | 1.00 (ref) | 148 | 1.00 (ref) |  |
   <5 | 358 | 1.16 (1.03-1.31) | 47 | 1.11 (0.80-1.55) |  |
   5 to less than 15 | 341 | 1.40 (1.23-1.58) | 51 | 1.52 (1.10-2.10) |  |
   ≥15 | 186 | 1.37 (1.17-1.61) | 40 | 2.28 (1.60-3.24) | 0.07 |
   Alcohol intake, continuous, RR (P trend)g |  | 1.05 (<0.001) |  | 1.12 (<0.001) | 0.02 |
Family history of breast cancer | Â | Â | Â | Â | Â |
   No | 1,553 | 1.00 (ref) | 227 | 1.00 (ref) |  |
   Yes | 394 | 1.71 (1.53-1.91) | 59 | 1.80 (1.35-2.39) |  |
Personal history of benign breast disease | Â | Â | Â | Â | 0.76 |
   No | 972 | 1.00 (ref) | 142 | 1.00 (ref) |  |
   Yes | 975 | 1.43 (1.30-1.56) | 144 | 1.41 (1.10-1.78) | 0.91 |