From: Sex steroid metabolism polymorphisms and mammographic density in pre- and early perimenopausal women
 | Mean | SD | Median | Number | % |
---|---|---|---|---|---|
Age at mammogram, years | 48.6 | 2.6 | 48.7 | Â | Â |
BMI, kg/m2 | 25.9 | 5.9 | 24.4 | Â | Â |
   <25 |  |  |  | 251 | 56 |
   25–30 |  |  |  | 111 | 25 |
   >30 |  |  |  | 89 | 20 |
Percentage mammographic density | 43.6 | 19.5 | 44.7 | Â | Â |
Age at first full-term birth | 28.1 | 5.5 | 28.0 | Â | Â |
Ethnicity | Â | Â | Â | Â | Â |
   African American |  |  |  | 26 | 6 |
   White |  |  |  | 219 | 49 |
   Chinese |  |  |  | 109 | 24 |
   Japanese |  |  |  | 97 | 22 |
Study site | Â | Â | Â | Â | Â |
   Oakland |  |  |  | 184 | 41 |
   Los Angeles |  |  |  | 169 | 37 |
   Pittsburgh |  |  |  | 98 | 22 |
Smoking currently | Â | Â | Â | 31 | 7 |
Menopausal status at time of mammogram | Â | Â | Â | Â | Â |
   Early perimenopausal |  |  |  | 332 | 74 |
   Premenopausal |  |  |  | 118 | 26 |
Parity | Â | Â | Â | Â | Â |
   0 |  |  |  | 77 | 17 |
   1 |  |  |  | 76 | 17 |
   2 |  |  |  | 196 | 43 |
   3 |  |  |  | 76 | 17 |
   4 |  |  |  | 19 | 4 |
   ≥ 5 |  |  |  | 7 | 2 |