Table 2 Association of alcohol use with percentage of breast tissue composition (log-transformed) in benign breast biopsy samples (Adjusted for age (continuous), BMI (continuous), a family history of breast cancer (Yes/No), menopausal status/postmenopausal hormone use (premenopausal, postmenopausal/no hormones, postmenopausal/past hormones, postmenopausal/current hormones, postmenopausal/unknown hormone use status), 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

− 0.02 (− 0.07; 0.03)

− 0.02 (− 0.03; − 0.01)

0.08 (− 0.03 × 10^–2; 0.15)

− 0.02 (− 0.03; − 0.01)

Categorical alcohol at BBD

Non-drinker

Ref

Ref

Ref

Ref

< 11 g/day (< 1 drink/day)

− 0.09 (− 0.18; 0.01)

− 0.02 (− 0.05; 0.29 × 10^–2)

0.14 (− 0.01; 0.28)

− 0.03 (− 0.05; − 0.01)

11–< 22 g/day (1–< 2 drinks/day)

− 0.07 (− 0.21; 0.08)

− 0.02 (− 0.06; 0.02)

0.19 (− 0.03; 0.41)

− 0.03 (− 0.06; 0.01)

≥ 22 g/day (≥ 2 drinks/day)

− 0.14 (− 0.33; 0.04)

− 0.08 (− 0.13; − 0.03)

0.30 (0.03; 0.57)

− 0.08 (− 0.13; − 0.04)

p-trend

0.25

0.01

0.04

< 0.01

Continuous cumulative average alcohol, per 11 g or one drink

− 0.02 (− 0.07; 0.04)

− 0.02 (− 0.03; − 0.46 × 10^–2)

0.07 (− 0.01; 0.15)

− 0.02 (− 0.03; − 0.01)

Cumulative average alcohol

Non-drinker

Ref

Ref

Ref

Ref

< 11 g/day (< 1 drink/day)

− 0.09 (− 0.19; 0.01)

− 0.02 (− 0.04; 0.01)

0.07 (− 0.08; 0.21)

− 0.03 (− 0.05; − 0.42 × 10^–2)

11–< 22 g/day (1–< 2 drinks/day)

− 0.05 (− 0.20; 0.09)

− 0.04 (− 0.08; − 0.08 × 10^–2)

0.19 (− 0.03; 0.40)

− 0.04 (− 0.08; − 0.31 × 10^–2)

≥ 22 g/day (≥ 2 drinks/day)

− 0.13 (− 0.32; 0.07)

− 0.08 (− 0.13; − 0.02)

0.32 (0.04; 0.61)

− 0.09 (− 0.14; − 0.04)

p-trend

0.46

< 0.01

0.01

< 0.001