Table 1.

Characteristics at blood collection of cases and their matched control subjects from the NHSII

Case subjects (n = 316)Control subjects (n = 633)
Age (y), mean (SD)45.3 (4.3)45.1 (4.3)
Parity, * mean (SD)2.2 (0.8)2.3 (1.0)
BMI at age 18 (kg/m2), mean (SD)20.9 (3.0)21.0 (2.7)
BMI at blood draw (kg/m2), mean (SD)25.4 (5.3)25.8 (6.1)
Had a follicular or luteal phase sample, %62.362.6
Premenopausal at blood collection, %75.675.5
Family history of breast cancer, %16.410.4
History of benign breast disease, %23.716.0
Took antidepressant medication, %13.012.0
Age at menarche ≥14 y, %15.817.5
Ever used oral contraceptives, %84.886.3
Current use of postmenopausal hormones, %18.717.9
Median prolactin (10th-90th percentile)Median prolactin (10th-90th percentile)
Follicular phase of the menstrual cycle (ng/mL) 13.4 (7.1-27.2)13.4 (7.3-27.3)
Luteal phase of the menstrual cycle (ng/mL) 16.2 (8.5-31.4)15.7 (8.4-30.0)
Average of follicular and luteal phases (ng/mL) §15.2 (8.9-28.5)15.3 (8.4-26.4)
Average of timed + untimed samples (ng/mL) 14.9 (8.9-28.4)14.5 (8.3-26.1)
  • * Among parous women only.

  • 193 cases and 384 controls have a sample in the follicular phase of the menstrual cycle.

  • 197 cases and 393 controls have a sample in the luteal phase of the menstrual cycle.

  • § 193 cases and 382 controls have a sample in both follicular and luteal phases of the menstrual cycle.

  • 312 cases and 620 controls that have either follicular and luteal phase samples (n = 193 cases/382 controls) or an untimed sample (premenopausal, 42 cases/83 controls; postmenopausal, 65 cases/135 controls; unknown menopausal status, 12 cases/20 controls).