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Table 1 Selected characteristics of the study population: The Norwegian EBBA-I study (n = 202)a

From: Polymorphisms in the estrogen receptor alpha gene (ESR1), daily cycling estrogen and mammographic density phenotypes.

Characteristics

Total study populationb

Age, years

30.7 (3.07)

Education, total years

16.1 (3.02)

Body compositionc

 BMI, kg/m2

24.4 (3.77)

 Waist, cm

79.5 (9.80)

 Tissue fat, %e

34.2 (7.62)

 Birth weight, g

3389 (561)

Reproductive factors

 Parity, No children

0.91 (1.13)

 Time since last birth among parous, years

4.72 (3.07)

 Age at menarche, years

13.1 (1.36)

 Cycle length, days

28.2 (3.17)

 Follicular phase length, days

14.9 (1.73)

 Luteal phase length, days

13.45 (1.73)

Salivary hormonesd

 Overall average 17β-estradiol, pmol/l

17.9 (8.79)

 Overall average progesterone, pmol/l

130.2 (68.3)

Serum hormonese

 Estradiol, pmol/l

146.7 (61.6)

 Progesterone, nmol/l

4.83 (6.29)

Lifestyle factors

 Previous use of oral contraceptives, %

82.7

 Leisure time, MET h/week

57.6 (88.6)

 Alcohol intake, units per week

2.89 (3.38)

 Current smokers, %

22.1

Mammogramsf

 Percent mammographic density, %

29.8 (19.0)

 Absolute mammographic density, cm2

34.7 (23.4)

  1. Abbreviations; BMI body mass index, EBBA-1 The Norwegian Energy Balance and Breast cancer Aspects Study 1
  2. aNumbers may vary due to missing information
  3. bValues are mean (SD) or percent
  4. cMeasurements at day 1–5 after onset of menstrual cycle
  5. dDaily saliva samples throughout an entire menstrual cycle
  6. eSerum samples at day 7–12 (mid-cycle phase)
  7. fMammograms and total tissue fat (DEXA) were taken at day 7–12 (mid-cycle phase) after onset of the menstrual cycle