Table 1.

Characteristics of premenopausal breast cancer cases and matched controls, New York University Women's Health Study

Characteristics	Cases (n = 377)	Controls (n = 377)
Mean age (SD), y	44.4 (4.8)	44.3 (4.8)
Mean age at diagnosis (SD), y	54.4 (6.5)	—
Mean age at menarche (SD), y	12.5 (1.5)	12.4 (1.5)
Mean age at first full-term pregnancy* (SD), y	26.5 (6.0)	24.8 (5.4)
Nulliparous, n (%)	145 (38%)	134 (36%)
Family history of breast cancer, n (%)	95 (25%)	77 (20%)
Ever use of oral contraceptives, n (%)†	193 (57%)	206 (62%)
Ever smoke cigarettes, n (%)‡	197 (55%)	176 (50%)
Mean height (SD), cm	163.2 (6.8)	162.6 (6.8)
Mean weight (SD), kg	64.2 (11.8)	63.6 (12.9)
Mean BMI (SD), kg/m2	24.1 (4.3)	24.0 (4.5)
Mean 2-OHE1 (SD), pg/mL	271.1 (161.8)	262.5 (154.1)
Mean 16α-OHE1 (SD), pg/mL	371.0 (117.1)	363.2 (108.7)
Mean 2-OHE1:16α-OHE1 ratio (SD)	0.79 (0.65)	0.76 (0.49)

Abbreviations: 16α-OHE1, 16α-hydroxyestrone; 2-OHE1, 2-hydroxyestrone.

^*P < 0.05. All other, P > 0.05.

^†Percentage of those whose oral contraceptives use history is known (89% of cases and 90% of controls).

^‡Percentage of those whose smoking status is known (95% of cases and 93% of controls).