Table 1.

Selected characteristics of breast cancer cases and their matched controls at blood collection (1995-1998) among women in the E3N cohort (n = 1,908)

Baseline characteristicsCases (n = 636)Controls (n = 1,272)
Mean (SD)
Age (y)56.9 (6.4)56.9 (6.4)
Age at menarche (y)12.7 (1.3)12.9 (1.4)
BMI23.8 (3.6)23.8 (3.8)
Age at menopause50.7 (3.7)50.7 (3.6)
Number of children1.9 (1.2)2.1 (1.2)
Recreational physical activity (METS-h/wk)51.0 (31.0)50.3 (22.6)
Alcohol intake (g/d)*12.0 (15.0)10.9 (13.8)
Serum 25(OH)D3 (ng/mL)24.4 (10.9)25.1 (11.0)
Serum calcium (mmol/L)2.29 (0.1)2.29 (0.1)
Serum PTH (pg/mL)26.7 (11.2)27.2 (19.1)
Serum estradiol (pmol/L)
    Premenopausal399.3 (234.3)349.2 (202.2)
    Postmenopausal125.6 (217.5)105.8 (205.5)
Serum progesterone (nmol/L)
    Premenopausal10.1 (15.2)9.0 (13.8)
    Postmenopausal4.0 (9.7)3.2 (7.7)
Calcium intake (mg)*1,017.5 (273.0)1,044.7 (289.9)
Vitamin D intake (μg)*2.4 (1.2)2.4 (1.2)
Total energy intake without alcohol (kcal)*21.2 (5.7)20.7 (5.6)
Mean UVB dose exposure (kJ/m2 by day)1.5 (0.2)1.5 (0.2)
N (%)
Postmenopausal489 (77.2)990 (77.2)
Family history of breast cancer
    No504 (79.3)1,104 (86.8)
    Yes132 (20.7)168 (13.2)
History of benign breast disease
    No243 (38.2)407 (32.0)
    Yes393 (61.8)865 (68.0)
Personal history of mammography
    No16 (2.5)51 (4.0)
    Yes620 (97.5)1,221 (96.0)
Smoking status
    Never350 (55.0)696 (54.7)
    Past217 (34.1)436 (34.2)
    Current69 (10.9)140 (11.1)
OC use
    No383 (60.2)761 (59.8)
    Yes253 (39.8)511 (40.2)
Use of postmenopausal MHT (among postmenopausal women)354 (72.4)687 (69.5)
Season
    Spring160 (25.2)279 (21.9)
    Summer112 (17.6)250 (19.6)
    Autumn188 (29.6)370 (29.1)
    Winter176 (27.7)373 (29.3)
Current use of calcium supplement
    No589 (92.6)1,183 (93.0)
    Yes47 (7.4)89 (7.0)
Current use of vitamin D supplement
    No602 (94.6)1,210 (95.1)
    Yes34 (4.4)62 (4.9)

NOTE: Assessed at the time of blood collection except where indicated.

Abbreviations: OC, oral contraceptive; MHT, menopausal hormone therapy.

  • *Assessed at the time of dietary questionnaire (1993). Calcium and vitamin D intakes estimated with residual methods.