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Table 1 Characteristics of the study population by alcohol consumption (drinks/week) in the past year (FFQ), Norwegian EBBA-I study (n = 202)a

From: Alcohol consumption, endogenous estrogen and mammographic density among premenopausal women

Variable Overall (n = 202)a Low consumers (<1 drink/week) (n = 66)a Moderate consumers (1–6 drinks/week) (n = 96)a High consumers (≥7 drinks/week) (n = 40)a p valueb
Characteristics      
 Age (years) 30.7 (3.07) 31.17 (2.86) 30.75 (3.16) 29.87 (3.09) 0.105
 Education (years) 16.1 (3.02) 15.82 (2.85) 15.98 (3.04) 16.70 (3.20) 0.324
Reproductive history
 Age at menarche (years) 13.1 (1.36) 12.75 (1.29) 13.21 (1.36) 13.48 (1.36) 0.016
 Cycle length (days) 28.2 (3.17) 28.40 (4.13) 28.01 (2.78) 28.98 (3.5) 0.314
 Parous (%) 51.2 61.2 46.0 27.5 0.002
 Number of children (n) 0.91 (1.13) 1.30 (1.29) 0.80 (0.98) 0.53 (0.99) 0.001
Anthropometric measuresc
 BMI (kg/m2) 24.4 (3.77) 24.47 (2.30) 24.55 (3.56) 23.92 (3.35) 0.665
 Waist (cm) 79.5 (9.80) 76.69 (11.26) 80.28 (9.56) 77.44 (7.47) 0.300
Lifestyle factors
 Leisure time (MET/hour/week) 57.6 (88.6) 48.09 (33.44) 63.23 (121.18) 59.59 (45.16) 0.552
Oral contraceptive use      
 Previous use (%) 82.7 76.1 85.0 90.0 0.119
 Sum use (years) 3.7 (3.7) 3.27 (3.72) 3.99 (3.69) 3.84 (3.63) 0.458
Alcohol consumption in the past year      
 Alcohol (drinks/week) 3.46 (4.10) 0.24 (0.28) 2.67 (1.46) 10.84 (2.87) <0.001
 Abstainers (%) 6.8     
Smoking habits      
 Current smokers (%) 22.1 11.9 25.0 32.5 0.030
 Former smokers (%) 45.4 32.8 50.0 55.0 0.037
Serum hormonesd
 Estradiol (pmol/l) 146.7 (61.6) 145.5 (70.49) 147.4 (62.80) 146.8 (41.04) 0.983
Salivary hormones
 Estradiol, overall averagee (pmol/l) 17.9 (8.79) 17.68 (7.65) 17.61 (9.29) 18.98 (9.40) 0.691
 Estradiol, mid-menstrualf (pmol/l) 18.20 (8.98) 17.69 (7.52) 18.05 (9.69) 19.01 (9.59) 0.839
Mammogramsg      
 Percent mammographic density (%) 29.8 (19.0) 28.08 (19.05) 27.33 (18.02) 38.51 (19.30) 0.005
 Absolute mammographic density (cm2) 34.7 (23.4) 31.57 (21.00) 31.89 (22.73) 46.77 (25.23) 0.001
  1. Data presented as mean (standard deviation). One drink or unit is equal to 10 g alcohol
  2. BMI body mass index, EBBA-I Norwegian Energy Balance and Breast Cancer Aspects I, FFQ food frequency questionnaire, MET metabolic equivalents
  3. aNumbers may vary owing to missing information
  4. bEquality between levels were tested using one-way analysis of variation for continuous variables and the chi-square test for binary variables
  5. cMeasurements at days 1–5 after onset of menstrual cycle
  6. dSerum samples in early follicular phase: days 1–5 after onset of menstrual cycle
  7. eDaily saliva samples throughout an entire menstrual cycle
  8. fDaily saliva samples mid menstrual cycle, aligned cycle days −7 to 6
  9. gMammograms were taken days 7–12 (mid-cycle phase)