|  |  | Cases | Controls |  | ||
---|---|---|---|---|---|---|---|
 |  |  | Number | % | Number | % |  |
 |  |  | 215 | 100 | 215 | 100 |  |
Breast cancer risk factors | Â | Â | Â | Â | Â | ||
   Family history of breast cancer |  |  |  |  |  | ||
 |  | yes | 67 | 31.2 | 55 | 25.6 | P = 0.199 |
 | BMI |  |  |  |  |  |  |
 |  | <25 | 89 | 41.4 | 95 | 44.2 |  |
 |  | 25-29 | 87 | 40.5 | 80 | 37.2 |  |
 |  | 30+ | 39 | 18.1 | 40 | 18.6 | P = 0.778 |
 |  | Mean (SD) |    26.2 (+/- 3.9) |    26.5 (+/- 4.8) |  | ||
 | Ever smoke |  |  |  |  |  | |
 |  | yes | 58 | 27.0 | 56 | 26.0 | P = 0.270 |
 | Age at menarche |  |  |  |  |  | |
 |  | <12 | 28 | 13.0 | 30 | 14.0 |  |
 |  | 12 | 58 | 27.0 | 49 | 22.8 |  |
 |  | 13 | 71 | 33.0 | 75 | 34.9 |  |
 |  | 14+ | 58 | 27.0 | 61 | 28.4 | P = 0.799 |
Reproductive history | Â | Â | Â | Â | Â | ||
   Never pregnant | 36 | 16.7 | 34 | 15.8 | P = 0.811 | ||
   Number of prenanciesa |  |  |  |  |  | ||
 |  | 1-2 | 102 | 57.0 | 83 | 45.9 |  |
 |  | 3-4 | 57 | 31.8 | 66 | 36.5 |  |
 |  | 5+ | 20 | 11.2 | 32 | 17.7 | P = 0.002 |
   Age at first pregnancya |  |  |  |  |  | ||
 |  | <20 | 24 | 13.4 | 34 | 18.8 |  |
 |  | 20-24 | 98 | 54.7 | 85 | 47.0 |  |
 |  | 25-29 | 38 | 21.2 | 41 | 22.7 |  |
 |  | 30+ | 19 | 10.6 | 21 | 11.6 | P = 0.415 |
 |  | mean (SD) |    23.9 (+/- 4.2) |    24.2 (+/-4.7) |  | ||
aamong parous women | Â | Â | Â | Â | Â | ||
   Age at menopause |  |  |  |  |  | ||
 |  | <45 | 40 | 18.6 | 38 | 17.7 |  |
 |  | 45 to 49 | 53 | 24.7 | 63 | 29.3 |  |
 |  | 50 to 54 | 89 | 41.4 | 91 | 42.3 |  |
 |  | 55+ | 20 | 9.3 | 10 | 4.7 |  |
 |  | unknown | 13 | 6.0 | 13 | 6.0 | P = 0.371 |
Years to breast cancer diagnosis (from blood draw) | Â | Â | Â | ||||
 |  | <1 | 7 | 3.3 |  |  |  |
 |  | 1 to <2 | 10 | 4.7 |  |  |  |
 |  | 2 to <3 | 18 | 8.4 |  |  |  |
 |  | 3 to <4 | 21 | 9.8 |  |  |  |
 |  | 4-<5 | 9 | 4.1 |  |  |  |
 |  | 5+ | 150 | 69.8 |  |  |  |
Matching factors | Â | Â | Â | Â | Â | ||
Age at blood collection | Â | Â | Â | Â | Â | ||
 |  | <55 | 60 | 27.9 | 62 | 28.8 |  |
 |  | 55 to 59 | 58 | 27.0 | 49 | 22.8 |  |
 |  | 60 to 64 | 45 | 20.9 | 43 | 20.0 |  |
 |  | 65 to 69 | 33 | 15.3 | 35 | 16.3 |  |
 |  | 70+ | 19 | 8.8 | 26 | 12.1 |  |
Type of menopause | Â | Â | Â | Â | Â | ||
 |  | Natural | 154 | 71.6 | 152 | 70.7 |  |
 |  | Ovariectomy | 26 | 12.1 | 28 | 13.0 |  |
 |  | Hysterectomy after age 54 | 22 | 10.2 | 22 | 10.2 |  |
 |  | Early hysterectomy <age 54 | 13 | 6.0 | 13 | 6.0 |  |
Years between menopause and blood collection | Â | Â | Â | Â | |||
 |  | <1 | 6 | 2.8 | 6 | 2.8 |  |
 |  | 1 to <2 | 15 | 7.0 | 17 | 7.9 |  |
 |  | 2 to <3 | 10 | 4.7 | 8 | 3.7 |  |
 |  | 3 to <4 | 9 | 4.2 | 9 | 4.2 |  |
 |  | 4+ | 175 | 81.4 | 171 | 79.5 |  |
 |  | unknown |  |  | 4 | 1.9 |  |
Time of blood collection | Â | Â | Â | Â | Â | ||
 |  | 11 am to 1 pm | 82 | 38.1 | 80 | 37.2 |  |
 |  | 2 pm to 5 pm | 62 | 28.8 | 60 | 27.9 |  |
 |  | 6 pm to 10 pm | 71 | 33.0 | 71 | 33.0 |  |
 |  | unknown |  |  | 4 | 1.9 |  |