Table 1.

Age-adjusted baseline (1995) characteristics (n=55,687).

Age, mean (SD)	38.7 (10.7)
Body mass index (kg/m2), mean (SD)	28.0 (6.7)
First-degree family history of breast cancer, %	8.9
Adult height (inches), %
≤63	30.3
64–65	27.6
66–67	25.3
68–69	11.3
≥70	5.4
Age at attained height (years)a, %
>17	13.5
13–17	56.3
<13	5.8
Unknown	24.4
Age at menarche (years), %
≥14	19.0
12–13	52.2
≤11	28.8
Parity and age at first birth
Nulliparous, %	35.1
Age at first birth (years), %
<20	22.1
20–24	23.1
≥25	18.4
Number of births, %
1	22.1
2	22.7
≥3	19.6
Recent use of oral contraceptives (<5 years), %	27.5
Menopausal status, %
Premenopausal	76.9
Postmenopausal	16.8
Unknown/missing	6.3
Estrogen plus progestin use, %
Never	96.2
<5 years duration	2.8
≥5 years duration	1.0
Education (years), %
≤12	19.0
13–15	36.1
16	23.8
≥17	21.0

Values are means or percentages standardized to the age distribution of the study population. Percentages may not sum to 100% due to missing data.

^aQueried in 1999.