Table 3 Association of alcohol use with percentage of breast tissue composition (log-transformed) in benign breast biopsy samples, premenopausal controls only (Adjusted for age (continuous), BMI (continuous), a family history of breast cancer (Yes/No), age at menarche (< 12, 12, 13, > 13, unknown), combined parity/age at first birth (parous with first birth before age 25, parous with first birth at or after age 25, nulliparous, unknown), BBD category (non-proliferative, proliferative without atypia, and proliferative with atypia), and NHS cohort (NHSI, NHSII))

Continuous alcohol at BBD per 11 g or one drink

0.01 (− 0.05; 0.07)

− 0.01 (− 0.03; 0.01)

0.02 (− 0.08; 0.11)

− 0.01 (− 0.02; 0.01)

Categorical alcohol at BBD

Non-drinker

Ref

Ref

Ref

Ref

< 11 g/day (< 1 drink/day)

− 0.09 (− 0.20; 0.02)

0.46 × 10^–2 (− 0.03; 0.04)

− 0.01 (− 0.18; 0.16)

− 0.27 × 10^–2 (− 0.03; 0.02)

11–< 22 g/day (1–< 2 drinks/day)

− 0.06 (− 0.24; 0.12)

0.01 (− 0.04; 0.06)

0.08 (− 0.19; 0.35)

− 0.01 (− 0.05; 0.04)

 ≥ 22 g/day (≥ 2 drinks/day)

− 0.24 × 10^–2 (− 0.22; 0.22)

− 0.05 (− 0.11; 0.02)

0.05 (− 0.29; 0.39)

− 0.03 (− 0.09; 0.02)

p-trend

0.83

0.20

0.57

0.26

Continuous cumulative average alcohol, per 11 g or one drink

0.01 (− 0.05; 0.08)

− 0.01 (− 0.02; 0.01)

− 0.49 × 10^–2 (− 0.10; 0.09)

− 0.36 × 10^–2 (− 0.02; 0.01)

Cumulative average alcohol

Non-drinker

Ref

Ref

Ref

Ref

< 11 g/day (< 1 drink/day)

− 0.06 (− 0.17; 0.06)

− 0.01 (− 0.04; 0.02)

0.03 (− 0.14; 0.20)

− 0.01 (− 0.04; 0.02)

11–< 22 g/day (1–< 2 drinks/day)

− 0.05 (− 0.23; 0.14)

− 0.02 (− 0.07; 0.03)

0.10 (− 0.17; 0.37)

− 0.03 (− 0.07; 0.02)

≥ 22 g/day (≥ 2 drinks/day)

− 0.03 (− 0.26; 0.20)

− 0.03 (− 0.10; 0.03)

0.15 (− 0.19; 0.50)

− 0.04 (− 0.09; 0.02)

p-trend

0.95

0.26

0.31

0.14