Table 1.

Characteristics at blood collection of cases and matched controls, stratified by having blood drawn <10 (proximate) or 10–20 years (distant) before diagnosis or reference date

A. Among all cases and controls (NHS and NHSII) who provided blood samples.
Distant BloodProximate Blood
CharacteristicCases (n = 953)Controls (n = 1,339)Cases (n = 2,468)Controls (n = 4,021)
Mean (SD)
Age, ya54.2 (7.6)54.7 (8.0)55.7 (10.0)54.3 (10.1)
BMI (kg/m2)25.6 (4.2)25.6 (4.9)25.6 (4.9)25.8 (5.2)
Age at menopause,yb49.5 (3.6)49.2 (3.8)49.9 (3.4)49.7 (3.4)
Age at menarche, y12.5 (1.4)12.6 (1.4)12.5 (1.5)12.5 (1.4)
Average childhood body sizec2.4 (1.2)2.5 (1.3)2.3 (1.2)2.5 (1.3)
Time from blood draw to diagnosis, y14.0 (2.8)NA5.1 (3.0)NA
n (%)
Postmenopausala547 (57.4)826 (61.7)1,445 (58.6)2,004 (49.8)
PMH usera,b280 (51.2)290 (35.1)875 (60.6)920 (45.9)
History of BBD410 (43.0)445 (33.2)1,046 (42.4)1,271 (31.6)
Family history of breast cancer135 (14.2)162 (12.1)439 (17.8)452 (11.2)
Parous848 (89.0)1,202 (89.8)2,147 (87.0)3,519 (87.5)
Oral steroid use16 (1.7)27 (1.2)48 (2.0)62 (1.5)
Antidepressant use76 (9.1)85 (7.7)213 (8.6)345 (8.6)
NHSa837 (87.8)1,107 (82.7)1,795 (72.7)2,677 (66.6)
Median (10th–90th percentile)
Prolactin, ng/mL10.7 (5.9–21.4)10.5 (5.9–22.6)11.7 (6.4–22.6)11.2 (6.3–22.6)
B. Among women in the NHS who provided two blood samples 10 years apart.
Cases (n = 518)Controls (n = 613)
CharacteristicDistant bloodProximate bloodDistant bloodProximate blood
Mean (SD)
Age, ya55.4 (6.9)66.5 (6.9)56.5 (6.8)67.5 (6.8)
BMI (kg/m2)25.6 (4.1)26.9 (5.0)25.4 (4.7)26.4 (5.1)
Age at menopause, yb49.6 (3.6)50.2 (4.1)49.1 (4.1)49.6 (4.4)
Age at menarche, y12.5 (1.4)12.6 (1.4)
Average childhood body sizec2.3 (1.2)2.5 (1.4)
Time from blood draw to diagnosis, y14.7 (2.5)3.6 (2.5)NANA
n (%)
Postmenopausala322 (62.1)509 (98.3)420 (68.5)604 (98.5)
PMH usera,b171 (53.1)348 (68.4)168 (40.0)344 (57.0)
History of BBD235 (45.4)325 (62.7)241 (39.3)336 (54.8)
Family history of breast cancer68 (13.1)112 (21.6)73 (11.9)102 (16.6)
Oral steroid use8 (1.6)6 (1.2)12 (2.0)8 (1.3)
Antidepressant use18 (3.5)66 (12.8)22 (3.6)67 (11.0)
Parous473 (91.3)572 (93.3)
Median (10th–90th percentile)
Prolactin, ng/mL10.6 (5.8–22.0)11.7 (6.4–19.9)10.3 (5.9–21.0)10.4 (6.5–20.9)
  • aMatching factor, cases who were postmenopausal and not taking hormones or premenopausal (NHS2) had two matched controls; all other cases had one matched control.

  • bAmong postmenopausal women.

  • cBased on the Stunkard scale of 9 body shapes; averaged for ages 5 and 10 years.