Table 1.
Characteristics of the study population by alcohol consumption (drinks/week) in the past year (FFQ), Norwegian EBBA-I study (n = 202)a
| 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 |
Data presented as mean (standard deviation). One drink or unit is equal to 10 g alcohol
BMI body mass index, EBBA-I Norwegian Energy Balance and Breast Cancer Aspects I, FFQ food frequency questionnaire, MET metabolic equivalents
aNumbers may vary owing to missing information
bEquality between levels were tested using one-way analysis of variation for continuous variables and the chi-square test for binary variables
cMeasurements at days 1–5 after onset of menstrual cycle
dSerum samples in early follicular phase: days 1–5 after onset of menstrual cycle
eDaily saliva samples throughout an entire menstrual cycle
fDaily saliva samples mid menstrual cycle, aligned cycle days −7 to 6
gMammograms were taken days 7–12 (mid-cycle phase)