Table 1.

Characteristics of cases and their matched controls in the Nurses’ Health Study (1992 – 2000) at blood collection

	Cases	Controls
No. of participants	801	801
Median (5th – 95th percentile)
Age, yearsa	57.3 (45.8 – 67.5)	57.3 (45.6 – 67.3)
Body mass index, kg/m2	24.4 (19.8 – 34.1)	24.4 (19.6 – 33.3)
Age at menarche, years	12 (10 – 15)	13 (11 – 15)
Alcohol intake, g/day	1.5 (0 – 27.5)	1.8 (0 – 20.6)
Parity (parous only)	3 (1 – 6)	3 (1 – 6)
Age at first birth, years (parous only)	24 (21 – 32)	24 (21 – 31)
Percentage (%)
Parous	90.6	94.4
History of benign breast disease	43.9	36.6
First degree family history of breast cancer	16.2	10.5
Current postmenopausal hormone usea	45.8	44.9
Postmenopausala	68.4	68.8

^aIndicates matching factor